NATL INST. OF STAND & TECH R.I.C

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^ecknlccil v2ote 251

RESEARCH ON CRYSTAL GROWTH

AND CHARACTERIZATION AT THE

NATIONAL BUREAU OF STANDARDS

JANUARY TO JUNE 1964

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
tiona! Bureau of Standards NOV 1 4 1968 151G71

THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assuring

maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. Its responsibilities include development and maintenance of the national stand- ards of measurement, and the provisions of means for making measurements consistent with those

standards; determination of physical constants and properties of materials; development of methods

for testing materials, mechanisms, and structures, and making such tests as may be necessary, particularly for government agencies; cooperation in the establishment of standard practices for incorporation in codes and specifications; advisory service to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the Government; assistance

to industry, business, and consumers in the development and acceptance of commercial standards and

simplified trade practice recommendations; administration of programs in cooperation with United

States business groups and standards organizations for the development of international standards of

practice; and maintenance of a clearinghouse for the collection and dissemination of scientific, technical, and engineering information. The scope of the Bureau's activities is suggested in the following

listing of its four Institutes and their organizational units. Institute for Basic Standards. Electricity. Metrology. Heat. Radiation Physics. Mechanics. Applied Mathematics. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radio Standards Laboratory: Radio Standards Physics; Radio Standards Engineering.** Office of Standard Ref- erence Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Materials. Reactor Radiations. Cryogenics.** Office of Standard Reference Materials.

Central Radio Propagation Laboratory.** Ionosphere Research and Propagation. Troposphere

and Space Telecommunications. Radio Systems. Upper Atmosphere and Space Physics.

Institute for Applied Technology. Textiles and Apparel Technology Center. Building Research.

Industrial Equipment. Information Technology. Performance Test Development. Instrumentation.

Transport Systems. Office of Technical Services. Office of Weights and Measures. Office of Engineering Standards. Office of Industrial Services.

* NBS Group, Joint Institute for Laboratory Astrophysics at the University of G)lorado. ** Located at Boulder, Colorado.
NATIONAL BUREAU OF STANDARDS

Technical Note 251

ISSUED OCTOBER 19, 1964

RESEARCH ON CRYSTAL GROWTH

AND CHARACTERIZATION AT THE

NATIONAL BUREAU OF STANDARDS

JANUARY TO JUNE 1964

Edited by Howard F. McMurdie

National Bureau of Standards

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.G., 20402 - Price 45 cents
Contents

1. Introduction 1

2. Crystal Growth 2 2.1 Growth of Dislocation-Free Metals from

the Melt 2 2.2 Kinetics of Growth of Crystals from

the Melt 3

2.3 Theory of Dendritic Crystallization 5

2.4 Crystal Growth Studies by Electron Field

Emission Techniques 5

2.5 Field-Emission Microscopy of Crystal

Growth Processes • 7 2.6 High-Temperature Crystal Growth 7 2.7 Crystal Growth from Solution 7 2.8 Hydrofluorothermal Growth of Crystalline

BeFg under HF Pressure 10

2.9 Crystal Growth and Structure Studies 10

2.10 Pseudopentagonal Twins in Electrodeposited

Copper Dendrites 12

2.11 Crystal Growth of Refractory Phases from

Solvents •»!( 12

2.12 Kinetics of Crystal Growth from Solution 13

2.13 Crystal Growth in Silica-Gel Medium 15

2.14 Spherulitic Growth in Relatively Pure

Systems •- 16

2.15 Homogeneous Nucleation Studies 16

2.16 Increase of Thickness with Time of Polyethylene Lamellae Crystallized from the

Melt- 17

2.17 Aspects of the Mechanism of Spherulitic

Crystallization of Polypropylene from

Solution 17

2.18 Kinetics of Spherulite Growth from Solution-- 19

2.19 Kinetics of Copolymer Crystallization 19

2.20 Theoretical Studies in Crystal-Whisker

Growth 20

3. Defect Characterization 23

3.1 Optical Properties, of "Pure" and Impure

Crystals 23

3.2 Irradiation Studies 23

3.3 Dislocation Studies in Metals 24

3.4 Stacking Fault Probabilities in Metals 24

3.5 Thermodynamics of Segregation of Solute Atoms

to Stacking Faults in FCC Binary Alloys 25

3.6 Characterization of Electrodeposited

Crystals 26

3.7 Defects in Thin Oxide Films 26

3.8 Report on Nuclear Magnetic Acoustic

Resonance 27

3.9 Laser Microprobe for Analysis of Very

Small Samples 28

3.10 Accurate Measurement of the Fundamental

Electrical Properties of Semiconductor

Crystals 30

li
3.11 Study of Crystal Defects 31

3.12 Magnetic Resonance Studies 33

3.13 Effect of Point Defects on the Dynamic

Properties of Crystals 37

3.14 Crystal Characterization by Double Crystal

X-ray Diffraction Topography 37

3.15 Magnetic-Resonance Studies -I 38

3.16 Automation of Single-Crystal X-ray Diffraction Intensity Measurements 39

Physical Properties of Crystalline Material 39

4.1 Crystal Orientation Methods 39

4.2 Crystal Symmetry and Crystal Properties 40

4.3 Studies in Solid-State Theory 40

4.4 Electronic Transport 41

4.5 Optical Constants of Materials from

1 to 1000 Rydbergs 41

4.6 Hall-Effect Measurements 42

4.7 Dielectric and Mechanical Properties 42

4.8 Electron-Spin Resonance of TransitionMetal Complex 43

4.9 Magnetic Properties of Salt Single Crystals

at Low Temperatures 44

4.10 Spin-Wave Study Using Single Crystals 45

4.11 Reference Data on Single-Crystal Elastic

Constants 45

4.12 Deformation and Fracture of Ionic

Crys tals 46

4.13 Nuclear Magnetic Resonance Studies in

Yttrium-Iron Garnets 46

4.14 Metal-Oxide Melting Point Standards 47

4.15 Soft X-ray Spectroscopy 47

4.16 Crystals of Organic Molecules 48

4.17 Experimental Determination of Atomic

Scattering Factors 49

4.18 Velocity of Sound in Ice Single Crystals 49

4.19 Density Measurements 50

4.20 Superconductivity in Niobium 51

4.21 Research on Superconducting Semiconductors-- 51

4.22 Optical Properties of Cadmium Sulfide

and Telluride 52

4.23 Soft X-ray Spectroscopy of Metals and

Alloys 52

Crystal Chemistry 53

5.1 Standard X-ray Diffraction Powder Patterns-- 53

5.2 Apparatus for High-Temperature Preparation

of Pure Crystalline Polymorphs 53

5.3 Fermi Resonance in Solids 54

5.4 Crystal Structure Analysis 54

5.5 Crystal Chemistry of Mineralized

Tissue 56

5.6 Phase Equilibria 56

5.7 Radial Distribution -Studies

of Glasses 57

5.8 Allotropy in the Rare Earth Metals 57

5.9 Infrared Studies of Inorganic Materials 58

5.10 Structure Models for Amorphous and Crystalline Phases of Simple Substances 58

111
5. 5.11 Crystal Chemistry of Silver Iodide 59

5.12 A New High-Resolution Small-Angle

X-ray Camera 59

5.13 Spectroscopy of Diatomic Impurities in

Rare-Gas Crystalline Matrices- 59

5.14 Crystal - Field Studies by Matrix

Spectroscopy 60

5.15 Phase Equilibria Determination with the

Aid of Crystal Structure Analysis 61

5.16 Ultrasonic Measurements at Pressure-Induced

Polymorphic Phase Changes 61

5.17 Microcomposition and Structure Characterization by Electronprobe Methods 62

6. Partial List of Participants 62

7. Literature References 69

XV
RESEARCH ON CRYSTAL GROWTH AND CHARACTERIZATION

AT THE NATIONAL BUREAU OF STANDARDS

JANUARY TO JUNE 19 64

Edited by

H. F. McMurdie

Abstract

The National Bureau of Standards with partial su5)port from the Advanced Research Projects Agency of the Department of Defense is con- tinuing a wide program of studies involving crystalline materials. These

include investigation of methods and theory of growth, study of detection

and effects of defects, determination of physical properties, refinement

of chemical analysis, and determination of stability relations and

atomic structure. The types of materials range from organic compounds,

through metals, and inorganic salts to refractory oxides. This Technical

Note, the fourth in the series, summarizes the progress of these various

projects from January to June, 1964, and lists the related publications

and participating scientists.

1 . INTRODUCTION

This is the fourth biannual report on crystal research at the

National Bureau of Standards. The three preceeding ones have been published as NBS Technical Notes 174, 197, and 236. These publications

present the background of the NBS effort in this area. Much of the work

described here is carried out with the support of the Advanced Research

Projects Agency. In anticipation of future technological demands in

crystal and material science, ARPA is encouraging the NBS to study the

techniques and theory of crystal growth, to characterize precisely the

crystals produced by various methods, and to extend precision measurement

to physical and chemical properties of crystals. The Bureau's own program in many aspects of this field is extensive and no effort is made

in the research descriptions below to separate the two efforts. Only

in the few instances in which financial support from other agencies

contributed to the program is an acknowledgement given.

The increase of the effort in crystal science by the ARPA cooperation

has resulted in an increased number of contacts and crosg-linking between participants in the program. This is a result in some cases of

having regularly scheduled group discussions of common problems and an exchange of visitors with other crystal science centers. The program as

a whole at the National Bureau of Standards is under the direction of

Dr. Harry C. Allen, Jr.
We wish to acknowledge the editorial assistance of Miss Lois L. Bardeen and Miss Betty L, Ragins of the Inorganic Materials Division and

the help given by the assistant editors who have represented the Bureau

Divisions as follows:

Electricity

Metrology

Heat

Analytical Chemistry

Mechanics

Polymers

Metallurgy

Inorganic Materials

Atomic Physics

Instrumentation

Physical Chemistry

Cryogenic Engineering

Radio Standards Physics

I. L. Cooter

D, V. Baker

J. F. Schooley

S. Rasberry

R. s. Marvin

E. Passaglia

R. L. Parker

F. A. Mauer

A. H. Kahn

J. c. French

D. E. Mann

R. L. Powell

J. L. Da Ike

2. CRYSTAL GROWTH

This chapter is concerned with

mechanisms and techniques of

crystal growth and dissolution.

2.1 Growth of Dislocation-Free Metals from the Melt

T. H. Orem, Crystallization of Metals Section

R. W. Dickson, Physical Properties Section

and

R. L. Parker, Crystallization of Metals Section

The background of this work is given in NBS Technical Notes 174,

Section 4.3, 197, Section 2.3, and 236, Section 2.1.

During the first three months of this reporting period, considerable

work was done in photographing, by the Lang technique, aluminum crystals

pulled from a melt of 99.9997o initial purity. Since it was considered

a possibility that much of the observed imperfections in the topographs

was due to surface strains and other surface imperfections in the carrotshaped crystals J they were studied both in the 'as-grown" condition and

after deep etching with aqua-regia to remove surface material. Approximately 25 photographs were taken on three such crystals, some of which

received several etchings with photographing after each etching. There were no significant differences between the etched and unetched crystals.

A considerable amount of work was done on an Al crystal received

from the Battelle Institute. The crystal had been pulled from a highpurity melt and had little visible oxide on its surface. It thus had a
very smooth bright surface. A total of 49 photographs were taken of

this crystal but no significant results obtained, due partly to the

fact that the crystal had considerable substructure.

A number of aluminum crystals were pulled from a melt of 99.9999%

initial purity (zone-refined) during this period. It is believed that

the use of the higher-purity aluminum, coupled with an improvement in

the crystal-pulling furnace, which minimized oxidation of the melt during the crystal-pulling process, has contributed significantly to the

production of better crystals.

Of approximately a dozen crystals grown, from the higher-purity

Al, using both monocrystalline and polycrystalline starting-seeds, two are believed to be of significant interest and are shown here. Figure 1

is a Lang topographic photograph of the tip of a crystal of near [001]

orientation. The decrease in dislocation density near the tip is obvious

Further along the crystal, the dislocation density increased conspicuously. Figure 2 is a crystal grown in such a manner that its axis is

parallel to [111]. Note the conical helix at the end of the high- imperfection (white) area. The pitch of the screw-like configuration approximates that of the crystal-pulling rate per revolution of the pulling

shaft. The low dislocation-density area of this crystal extends inward

from the tip of the crystal to the apex of the conical helix, a distance

of oi 1.6 mm, at which point the diameter is ?a .4 mm. The crystals used

to obtain Figures 1 and 2 are the only Al ones we have grown and examined which show a contrast in reflection intensity near the tip such that

individual dislocations can be resolved. They both show that there is a critical diameter above which the imperfections are so dense as to be

incapable of resolution. Both topographs were obtained by use of the

Rigaku-Denki microfocus X-ray unit and camera. Other investigators have

found that in the growth of carrot-shaped aluminum crystals by pulling

from the melt, .5 mm is the diameter below which a crystal will exhibit

a decrease in dislocation density.

Confirmation of the configuration in the tip of the crystal in

Figure 2 may be seen in Figure 3, a double-crystal diffraction topograph

of the same area of the crystal, taken by R. D . Deslattes, Crystal

Chemis try Sect ion

.

Current work involves the production and characterization of

additional aluminum crystals with a view toward further investigation of

this crystal diameter effect.

2.2 Kinetics of Growth of Crystals from the Melt

J. G. Early and R. L. Parker,

Crystallization of Metals Section

As stated in previous technical notes (see NBS Technical Notes 174,

Section 4.4, 197, Section 2.4, and 236, Section 2.?), the objective of

this project is to study the kinetics of the growth of a solid from the

melt, and to correlate this with the effect of crystal orientation.

Several experiments have been made with a single crystal of tin

grown from tin having an as-received purity of 99. 9997... The results

seem to indicate that sufficient solute is being rejected into the

liquid at the solid-liquid interface to cause constitutional supercooling

which partially masks the kinetic effects at the interface. Further

experiments are planned using 99.99997o tin as the raw material for

3
Fig. 1. Lang topographic photograph of the tip of an Al

crystal with the axis parallel to [001] direction,

Fig. 2. Lang topographic photograph of the tip of an Al

crystal with the axis parallel to [111].

Fig. 3. A double-crystal diffraction topograph of the

crystal shown in Figure 2.
growing additional single crystals in an effort to eliminate solute

effects. In addition, a zone-refining apparatus is being purchased to

aid in the preparation of high-purity materials for subsequent experiments .

2.3 Theory of Dendritic Crystallization

S. R. Coriell and R. L. Parker,

Crystallization of Metals Section

In a recent article, Mullins and Sekerka [J. Appl. Phys . , 34, 323

(1963)] have studied the stability of shape of a spherical particle

growing in a supersaturated solution or a supercooled liquid. They

found that when the radius of the sphere exceeded a certain radius R

the spherical shape was not stable. A question arises as to whether^

this type of instability can explain the formation of branches on dendrites. Sufficiently far from the dentrite tip, the dendrite shape

may be approximated as a cylinder. We have studied the stability of

shape of an infinite cylinder using the method of Mullins and Sekerka.

It is found that the circular cross -section of a cylinder is stable

when its radius is below, and unstable when its radius is above a certain radius R . This is analogous to the result for a sphere. For

the cylinder, however, R is a function of the supercooling, while for

the sphere, R is independent of the supercooling. It is also found

that the cylinder is always unstable with respect to certain perturbations which decrease the surface to volume ratio of the cylinder. An

article, "Stability of a Cylinder Growing in a Diffusion Field", has

been prepared for publication. (Coriell and Parker, 1964)

The preceding treatment assumes local equilibrium at the interface

and that the surface free energy is isotropic. It would be highly

desirable to study the stability of shapes without these assumptions.

The possibility of applying the Mullins and Sekerka method to the

stability of a more realistic shape (e. g. a parabola of revolution) is

being considered,

2.4 Crystal Growth Studies by Electron

Field Emission Techniques

S. C. Hardy and R. L. Parker,

Crystallization of Metals Section

The heterogeneous nucleation of Hg crystals from the vapor phase

is being studies in an electron field emission microscope. The W

field emission tip provides the substrate upon which the nuclei grow.

The stable nuclei appear as bright spots superposed on the pattern

from the tip. The emission patterns of a clears W Ip and of the same

tip after nucleation has occurred are shown in r igures 4 and 5, respectively. Nucleation takes place about, but not on, the Oil and 112 type

planes. The nuclei are cap-shaped. The time required to form nuclei

is being measured over a range of vapor pressures and substrate temperature.
Fig. 4. Emission pattern of a clean W tip,

Fig. 5. Eriiission pattern of the same W tip as Figure 4

after nucleatlon of Hg has occurred.
2.5 Field-Emission Microscopy of

Crystal Growth Processes

A. J. Melmed,

Corrosion Section

The writer began work at the National Bureau of Standards in

March, 1964. Laboratory facilities have been constructed and tested,

and experimental work begun. Two investigations are in progress:

(1) A study of the expitaxial growth of Fe crystals, from the vapor

phase, on W field emitters, and (2) Measurements of the activation

energy for Cu surface self-diffusion from the fie Id-deformat ion and

from zero field annealing rates of Cu crystals expitaxially grown on W field emitters.

2.6 High-Temperature Crystal Growth*

W. S. Brower,

Crystal Chemistry Section

The use of direct electromagnetic heating using high frequency RF

power has been successfully used to heat NiO to its melting point. This

heating method has been used to pass molten zones through polycrysfcalline

NiO rods in the usual floating zone arrangement. Some NiO rods have

been zoned a total of eight passes, with no significant improvement in

crystallite size from the first to last pass. Current efforts are being directed toward reducing the thermal cracking and improving the

temperature control in order to obtain single crystals.

Crystal growth is underway with the use of the Verneuil technique.

In particular, pre-oriented crystals of chromium-doped rutile, TiOg

,

have been grown.

2.7 Crystal Growth from Solution

J. L. Torgesen and A. T. Horton,

Crystal Chemistry Section

The growth of large single crystals from solution by temperatureprogram techniques (see NBS Technical Notes 174, Section 4.5, 197,

Section 2.5, and 236, Section 2.8) has been continued with the production of specimens of ammonium.

d

ihydrogen phosphate and sodium chlorate.

Grown in the presence of Cu ion impurity, sodium chlorate undergoes

a marked change in habit with the {110} and [111] forms in much greater predominance than characteristic of growth from pure solution. Although it was reported previously. (NBS Technical Note 236, Section,

2.8) that some differences in Cu deposition occur dependent on growth

direction, more precise analysis of recently harvested crystals show

this is not the case. From, solution containing 0.18 weight percent

Cu ion, deposition of Cu on [100], [110], and fill] amounts to

* This work is partially supported by the Atomic Energy Commission.
0.6 (±0.2) ppm with no significant differences outside the precision of

the analysis to be noted for these three regions of the crystals.

Potassium acid phthalate (KAP) single crystals are presently being

grown by temperature-dropping and isothermal techniques. The goal

is to produce crystals of adequate size and perfection for long-wave

length X-ray spectroscopy (compare Section 4.15). In an effort to avoid

damage to seed crystals by drilling or gluing (for mounting purposes)

and to produce crystals as nearly strain-free as possible, seed crystals are grown directly on Teflon sleeve mounts, which are then transferred

to the crystal tree for further growth in the large crystal baths.

Volunteer growth has been troublesome, especially in the isothermal

solvent-evaporation equipment [Karpenko et al., Sov. Phys . Cryst., 6, 120

(1961) ]. Excessive nucleation and growth of crystals in the solution

surface requires revision of the system to return an appreciable portion

of the condensing solvent to the surface, hence decreasing surface supersaturation, to provide a baffle system or to decrease suDersaturation'

in the growth chamber generally [Sampson and Di Pietro, Rev. Sci, Intr.

34, 1150 (1963)].

Characterization of ADP crystals by rocking curves and x-ray

diffraction topography (see Section 4.15) has continued with the

examination of (100), (101), and (110) sections. The careful preparation

of crystal sections by string-sawing with water as the solvent, followed

by etch-polishing with ethyl alcohol-water mixtures (80:20 by volume)

produces specimens in which high intrinsic perfection is retained. Flat

etch-polishing is accomplished by rotating and advancing the crystal

specimen closely adjacent to, but not touching, a rotating glass plate

over which flows a thin film of the alcohol-water etchant. A photograph of the etch-polish device is shown in Figure 6. The surfaces

thus produced possess diffraction characteristics believed to approach

those inherent in the crystals as grown and are tentatively taken to

be representative of the bulk crystal. The general uniformity of the

diffraction topographs shows the absence of significant strain and

regions of 1 cm^ or more to be free of defect images

.

It is hoped that etch-pit studies may corroborate the results

which have been obtained on crystal perfection of ADP by x-ray methods.

Etch-polishing by the procedure noted above, but with 10 drops of

saturated solution of ferric chloride in concentrated hydrochloric acid

added per liter of aicohol-water etchant, produces etch-pits on [100}

illustrated in Figure 7. The pits are well defined, showing tetragonal

symmetry with four [101} facets extant. On flOl} the same etchant produces triangular etch-pits, shown in Figure 8, defined by three [101}

facets. A saturated solution of potass ium-acid-phthalate has also

proved effective in developing etch-pits on the [100} face of ADP.

A momentary dip in the solution, followed by immediate rinsing in

isopropyl alcohol, results in etch-pits shown in Figure 9. Good definition and tetragonal symmetry are apparent. A comparison of the

patterns and density of etch-pits with those of defect images in x-ray

topographs of the same specimens is presently in progress.

Work on the growth of oxalic acid single crystals from solution

in glacial acetic acid and in acetone-water mixtures has been concluded.

The details of this investigation are reported in a paper (Torgesen and

Strassburger, 1964) which has been accepted for publication in Science .
Fig. 6. Etch-polish assembly,

Fig. 7. Etch-pits in ADP [100].

Etchant: Ethyl alcoholwater mixture (80:20 by

volume) containing 10

drops per liter of a saturated solution of

ferric chloride in cone,

hydrochloric acid.

Fig. 9. Etch-pits in ADP [100].

Etchant: Saturated solution

of potassium acid phthalate.

Fig. 8. Etch-pits in ADP [101]

Etchant: Same as for

Figure 7.
2.8 Hydrofluorothermal Growth of

Crystalline BeFg under HF Pressure

A. R. Glasgow, Jr.,

Analysis and Purification Section

Researches were performed in the development of a "hydrofluorothermal" process for the growth of BeFg crystals in a platinum-lined steel

bomb under pressures of 30-50 atmospheres of HF. (Tech. Note 197,

Section 5.10). This method is similar to the hydrothermal growths of

quartz from S iOg

.

A major bottle-neck in the development of this process has been

the anhydrous addition of HF to a closed bomb. The technique under

development is the anhydrous addition of HF from a Pt and Pt-Ir

ampoule with a thin-rupture disc (.001 inch) of platinum. The HF is

added, sealed, and weighed in the ampoule where the pressure never

exceeds 2 atmospheres. However, after placement in the closed bomb and

heating to 100 to 150 °C, the internal pressure of HF inside the ampoule

increases to 10-30 atmospheres. This causes the disc to rupture and

the HF to be released to the contents of the bomb.

The necessary Pt and Pt-iridium parts have been received. The

technique of transfer and sealing is nearing perfection. Actual growths

by this method are expected later this year. A cross -sectional view

with a legend describing the parts of the rupture-disc ampoule is

shown in the accompanying drawing. Figure 10.

2.9 Crystal Growth and Structure Studies

D. E. Roberts,

Solid State Physics Section

Single crystals of rutile (TiOg) are being grown, doped, and prepared as required. Measurements are made of transport, optical, magnetic, mechanical, and resonance properties. Growth is by the flamefusion technique, but methods of flux or solvent growth are being tried.

Dopants include more than 15 elements which have been mixed into the

powder from which boules are grown.

A number of materials have been prepared for superconductivity

studies. These include MggBig, SnSe, SnSeg, Sb^Seg , InTeg , AggSe,

AuSbg , BigTea , GaTe, and M0O3

.

Formerly (Tech. Note 236, Section 2.7) we reported CdS crystals

grown from the vapor in needle and platelet form up to a few m.m. in

dimensions. Because of their adaptability for optical measurement the

present effort is being made to obtain platelets of a larger size.

Other vapor-grown materials include CdTe, CdO, and M0O3

.

10
T"^

I

II /

Platinum tube 1/8 inch O.D,

.010 inch wall

Platinum- iridium body 90% Pt

and 10% Ir alloy

C. Platinum- iridium ring 90% pt

and 10% Ir alloy

D. Platinum disc, foil .001 inch

thick soldered to B and C

E. Position where tube is cut off

after filling with HF and closing tube with pliens

Fig. 10. Rupture-Disc -Ampoule

11
2.10 Pseudopentagonal Twins in Electrodeposited

Copper Dendrites

F. Ogburn,

Electrolysis and Metal Deposition Section,

and

B. Paretzkin and H. S. Peiser,

Crystal Chemistry Section

This work was described in NBS Technical Note 236, Section 2.17,

The results have since been published (Ogburn, Paretzkin, and

Peiser, 1964).

2.11 Crystal Growth of Refractory

Phases from Solvents

H. S. Parker,

Crystal Chemistry Section

This project was initiated in December, 1963. The objectives are

to develop and evaluate methods of growth of highly perfect crystals

at temperatures below the melting point of the crystal. The use of

temperatures at or near the melting point of the crystal must unavoidably introduce physical lattice defects from thermal agitation alone.

Additionally, crystals of many substances are difficult or impossible

to grow at temperatures approaching the melting point because of high

vapor pressure, incongruent melting or undesirable phase changes.

The method being considered here involves a traveling solution

zone in a specimen placed in a temperature gradient. The method in

its essentials, first proposed by Pfann ["Zone Melting", Wiley & Sons,

New York, 1958] has been analyzed theoretically by W. A. Tiller

[J. of Appl. Phys. 34, 2757-2762 (1963)] and has been applied success- fully by A. I. Mlavsky and M. Weinstein [J. of Appl. Phys. 34, 2885-

2892 (1963)] to the growth of GaAs and SiC.

The necessary equipment has been assembled and a series of ex- periments growing zinc oxide are currently in progress. The experimental configuration involves a single-crystal seed of zinc oxide separated

from the polycrystalline source material be a solvent layer approximately 0.2 to 0.3 mm in thickness with the resulting "sandwich

placed in a suitable temperature gradient. Of the various solvents

investigated, evidence of growth thus far has been obtained only through

the use of PbMoO^ as a solvent, and operating temperatures of the

order of 1100 to 1200 °C . Efforts to find more suitable solvents are continuing, and attempts will be made to optimize the solvent thickness

and operating temperature using PbMoO^

.

12
2.12 Kinetics of Crystal Growth from Solution

R. W. Jackson and J. L. Torgesen,

Crystal Chemistry Section

The purpose of this investigation is to study the mechanism of

growth of crystals from solution and how it is influenced by supersaturation and the presence of impurities

.

Molecules or ions arriving at a crystal face by diffusion from the

solution will not be incorporated into the lattice unless a growth step

exists on the surface. The old theories of crystal growth [H. E. Buckley,

Crystal Growth (John Wiley & Sons, New York, 1951 ) Chapter 6] suggest

that the growth step originates as a surface nucleus, which, when larger

than a certain critical size, will grow until the whole face is covered.

Growth then ceases until a new surface nucleus is formed. It is known

that crystal growth, once initiated can proceed at low supersaturation

where the probability of surface nucleation is small. Modern theories

[Cabrera and Vermilyea, in Growth and Perfection of Crystals , Doremus,

Robert, and Turnball, eds . (John Wiley & Sons, New York, 1958) p. 393]

propose that a continuing source of growth steps is provided by imperfections in the crystal in the form of screw dislocations.

The examination of dry crystal surfaces after growth by reflectionphase-contrast microscopy may fail to reveal growth steps or evidence of

dislocations. Only when the growth steps are large and the crystal differs considerably in refractive index from the solution in which it is

growing are growth steps visible by transmitted light with the light

microscope. A more sensitive method, used successfully to observe growth

layers on growing sucrose crystals [Albon and Dunning, Acta. Cryst., 12,

219 (1959)] employs microscopic observations with reflected light. This

method is being used in the present investigation to study the growth of

ADP crystals from aqueous solution.

Small crystals of ADP are being grown by feeding with supersaturated

solution in a special cell, mounted and temperature-controlled on the ro- tating stage of a micrdscope. By reflected light and at a magnification

of SOX, the surface features of the f lOOjandflOl] faces are being examined

during growth. It has been found necessary to use a low-power objective

to provide sufficient working distance and the maximum amount of light.

From pure ADP solution, the deposition of crystalline material on flOO] proceeds by the movement of spiral steps which are slightly elliptical in shape and emanate from screw dislocation centers. The longer

axis of the elliptical spiral appears to be at right angles to the c-axis

of the crystal. Photomicrographs of the spirals have been prepared and

time-lapse films have been taken, recording the movement of steps across

the face. A typical single-dislocation spiral is shown in Figure 11. A

Frank-Read source (neighboring screw dislocations of opposite hand) forming closed loops, is shown in Figure 12.

No dislocation centers have been observed so far on the [101] face.

Growth on this surface apparently proceeds by the movement of essentially

straight steps from the edges of the face towards the center. Figure 13

illustrates the phenomenon.

With chromic ion impurity in the solution, the spiral steps on

[100] assume an almost rectangular shape with the longer dimension

13
Fig. 11. Growth spiral on ADP {100}. Fig. 12. Frank-Read source on ADP ±

flOOJ.

Fig. 13. Layer growth on ADP {101}. Fig. 14. Dissolution etch-pits on ADP [101}

.

14
iagain at right angles to the c-axis . At approximately the same supersaturation, the steps move much faster than in pure ADP solution because

the number of dislocation sites is considerably increased.

Some observations have been made on the crystal faces during dissolution, the temperature of the growth cell having been raised above

ithe saturation temperature. Etch pits have been seen to occur on both

[100] and [101} faces. A typical arrangement on [101] is shown in Figure

14.

2.13 Crystal Growth in Silica-Gel Medium

J. L. Torgesen and A. J. Sober,

Crystal Chemistry Section

Single crystals of salts, sparingly soluble in water, can be

grown in silica-gel medium [Holmes, J. Franklin Inst., 184 , 743 (1917)]

by the slow interdiffusion of the component ions (see Technical Notes 197,

Section 2.5, and 236, Section 2.8). The method is most applicable to

materials having solubilities in water of the order of 0.01 percent. Copper tartrate, calcium tartrate, lead mono-and di-iodide, and calcium sulfate dihydrate have been grown as single crystals several millimeters in

size, some up to 1 cm in longest dimension.

The occlusion of silica in the crystals may occur to a considerable

extent. The analysis of copper tartrate single crystals shows the pre- sence of 0.047o silica.

Recent experiments have included the growth of cuprous chloride by

the reduction of cupric ion with an appropriate reducing agent in the

presence of excess chloride ion. Whereas, as reported previously, the

reduction of cupric sulfate by interdiffusion in the silica-gel with hydroxy lamine hydrochloride produces both fern- like tetrahedral dendrites

of copper metal, the reduction of cupric chloride leads to the growth of

crystalline cuprous chloride. The material grows as both fern-like

dendrites and as well-developed, optically clear tetrahedra up to 3 mm on edge. An interesting feature is the growth of the dendrites in regions

immediately adjacent to the container (pyrex test-tube) walls, the

tetrahedra appearing in the more central portions of the gel. Similar

results ha.ve been obtained with 1-ascorbic acid as the reductant, while

hydrazine dihydrochoride, contributing to a lower pH in the system, re- quires initial gels of lower acidity (solubility of cuprous chloride

increases in strongly-acid systems) . Deaeration of these oxidation-reduction systems with tank nitrogen is being employed to avoid air-oxidation of the reducing agents.

Ways and means to inhibit excessive nucleation (which contributes to

large numbers of small crystals) are presently being explored. Although

it is recognized that the polymeric silicic-acid chains which comprise

the gel may provide nucleation sites in over-abundance, the component

solutions of the systems are being ultra-filtered (various pore sizes)

to decrease the concentration of motes, which are surely sites for heterogeneous nucleation. In addition, the effects of a "neutral" gel zone (containing initially no reacting ions) between the ion-source regions are under study.

15
2.14 Spherulitic Growth in Relatively

Pure Systems

G. S. Ross and L. J. Frolen,

Polymers Division

Studies of both single crystal and spherulitic growth from highlypurified melts of a homologous series of diphenyl alkanes are continuing

(see Technical Note 236, Section 2.9). Photomicroscopic observations of

supercooled melts of 1, 2 diphenylethane (m.p. 52 °C) 1, 4 diphenylbutane

(m.p. 52 °C) and 1, 6 diphenylhexane (m.p. -12 °C) indicate the existence

in each case of a maximum growth-velocity with increasing undercooling.

It further appears that the spherulitic mode of crystal growth occurs at

undercoolings greater than that corresponding to the growth-rate maximum

while single crystals have been observed to grow at temperatures closer

to the melting point. Some of these observations have been recorded

on color film, an edited version of which is available.

The next step in this investigation requires the quantitative determination of growth rates as functions of undercooling. The crystallographic identity of the spherulitic and single-crystal forms has yet to

be demonstrated. Attempts to do so are now in progress.

2.15 Homogeneous Nucleation Studies

F. Gornick, G. S. Ross, and

L. J. Frolen,

Polymers Division

During the current report period, a microphotographic facility for

time-lapse as well as cinematic photography has been assembled from both

commercially-obtained and NBS built components . The purpose to be served

by this unit is the photographic observation of freezing in immobilized

supercooled liquid droplets on an isothermal hot-stage (see NBS Technical

Note 197, Section 2.8). The hot-stage has been tested and shown to be

capable of regulation to within 0.01 °C or better for indefinite service

in the temperature range 30 " to 150 °C. A separate report on the performance and details of construction of this hot-stage is now in preparation.

Techniques for the preparation of micron-sized cooled polyethylene

droplets are under investigation. Facilities for column fractionation,

viscosity determination and high- temperature purification have been ac- quired and continue to be developed.

A theoretical treatment of the statistics of droplet nucleation in a system subject concurrently to homogeneous and heterogeneous nucleation

has been completed and will be submitted for publication in the near

future.

16
2.16 Increase of Thickness with Time

of Polyethylene Lamellae Crystallized

from the Melt

J . J . Weeks

,

Polymers Division

Previously it was assumed that the observed increase of melting

temperature of Marlex 50 polyethylene with time of crystallization was a result of thickening of the lamellar crystals [J.J. Weeks (J. Research

NBS 67A, 441 (1963)]. Fischer and Schmidt [Angew. Chem. Internat. Edit.,

jL. 488 (1962) ] have obtained x-ray diffraction evidence showing that the

low-angle spacing (L^ and Lg) in bulk polyethylene increases with time of

annealing at temperatures above the crystallization temperature, T . It was felt that this type of measurement should be made at T during^the

crystallization. Using the Kratky low-angle camera, values of two spacings were obtained at T = 128.2 °C as a function of crystallization time

on the same Marlex 50 t^at was used for melting-point studies. The re- sults show that both L^ and Lg increase with time during primary (Stage 1)

crystallization and then level off. This agrees qualitatively with the

melting temperature studies. A short note has been prepared for early

publication.

2.17 Aspects of the Mechanism of Spherulitic

Crystallization of Polypropylene

from Solution

F. I^ury,

Polymer Physics Section

It has been previously reported that isotatic poljrpropylene crystallizes from f% solutions of the polymer in amyl acetate at 115 °C, in

the form of pseudopolyhedral aggregates. The habit of these aggregates

is similar to that exhibited under the optical microscope by the initial,

less accessible, transient structures which develop during the early

stages of formation of monoclinic polypropylene apherulites from solution and from the melt (see Technical Note 236, Section 2.14). The determination of the fine structure and mechanism of growth of these model

aggregates grown from amyl acetate has been pursued. Further insight into these aspects has been obtained by isolating the aggregates from the

mother liquor at an early stage of growth (under isothermal conditions)

and subsequently examining thiem in widely different perspectives under

the electron microscope. Electron micrographs representing normal and

end-on views of these essentially planar aggregates are shown in Figures

15a and 15 b, They possess a distinctly dendritic morphology as clearly

revealed in Figure 15a; further, their narrow (150-200A) diagonally

oriented branches exhibit a lamellar habit when viewed along the plane

of the aggregates (note the lamellar structures at the extremities of the

aggregate shown in Figure 15b)

.

An acillary study of the birefringence of the aggregates coupled

with the structural features briefly summarized folded within the individual branches, the extended interfold-helical segments of the molecules being oriented preferentially parallel to plane of the aggregates

and normal to their longer lateral edges . An attempt is being made to

17
Fig. 15. Transmission electron micrographs of

different aspects of similar polypropylene

aggregates fomed within nine hours of

crystallizing the polymer from a 3/4% solution in amy! acetate at 115 °C.. (a) The

aggregate is oriented with the plane of

preferential development normal to the

direction of viewing, (b) The aggregate

is viewed parallel to the plane of preferential development. (x 30,200)

18
determine the exact lattice orientations within the constituent branches.

The possibility that these aggregates are twinned dendrites is envisioned.

2.18 Kinetics of Spherulite Growth from Solution

G. M. Martin and E. Passaglia,

Poljrmer Physics Section

The rate of spherulite growth of polypropylene from a TL solution

in cis-decalin has been measured by dilatmetric methods. The isotherms

do not follow an Avrami law accurately, the deviations being in the

direction expected by theory [F . Gornick and L. Mandelkern, J. Appl. Phys

33_, 907 (1962) ]. However, the growth rate appears to be exponentially

dependent on the reciprocal of the supercooling, as is customary.

Preliminary measurements indicate that the radial growth is not

linear in time. This also is to be expected on the basis of theory.

2.19 Kinetics of Copolymer Crystallization

R. K. Eby,

Polymer Physics Section

There is quite a bit of evidence that some copolymers form lamellar crystals with the comonomer units incorporated within the lattice

as point defects (Eby, 1964; also see Eby and Bolz, Technical Note 236,

Section 5.13). One of the phenomena that this model must be able to

account for is the fact that when a series of copoljrmers are cooled

from the melt at about the same rate, the copolymers with a higher con- centration of comonomer units form thinner lamellae [H. Hendue, Ergeb.

der Exakt. Naturwiss., 31, 363 (1959)]. While the explanation of this

fact is straight- forwar^in a model based on exclusion of comonomer

units from the crystal, it is not so obvious with the model presented

above. We have approached this problem using the method of Hoffman and

Lauritzen [J. Research NBS 65A , 297 (1961)], and taking account of the

effect of the point defects on the various thermodynamic quantities

involved (Eby, 1963) . Initial results obtained with the simplest asumptions indicate a dependence of lamella thickness on point-defect concentration.

19
2.20 Theoretical Studies in Crystal-Whisker Growth

J. A. Simmons, R. E. Howard,

Metal Physics Section

R. L. Parker,

Crystallization of Metals Section

and

H. Oser,

Applied Mathematics Division

This work summarized in NBS Technical Note 236, Section 2.2 was presented at the Philadelphia meeting of the APS and is published

(Simmons, Parker, and Howard, 1964).

From the asymptotic formula for linear growth and the face that

x(t) is always increasing the inequality

D^ X

T

(1 + 1 ) yr

permits lower bounds for the surface self-diffusion coefficient on close-packed planes to be computed from experimental data on whisker

growth. Reasonable bounds were obtained by this method for 13 metals.

Results from the preliminary computer program mentioned in NBS

Technical Note 197, Section 2.16, showed that a step-wise linear

approximation to the growth curve was inadequate due to the extreme

sensitivity of the concentration profile near the whisker tip to the

rate of growth x(t) . This resulted in unstable numerical behavior of

many of the integrals involved. Consequently, the computer program

has been totally revised in order to obtain sufficient accuracy for

both the whisker- growth curves and surface-concentration profiles.

The organization of the program is indicated in the following

s cheme

:

I

Main program

Input, Output

step-by-step

procedure

x^

Subroutine 1

Ax=F [x(t),

^^(x,t)]

Subroutine 2

[u(x,t + nh) ] = G[x(t), u(x,t)]

Subroutine 3

Numerical

Integration

Logical Organization of

Computer Program

20
The main program controls input and output of parameters and

results, provides interpolation formulas for the effective evaluation of

the integrals in the subroutines, and controls either the step-by-step

computation of the growth increment Ax during the time step At or the

concentration profile u(x,t) by calling the appropriate subroutine 1 or 2 respectively. The third subroutine is an integration routine which re- cords the numerical error of the result for control purposes . The incrementsAx are computed in Subroutine 1 as follows:

o

^^j ^i[ ^^\ /

o

^

/

This equation arises from the conservation of mass and the implicit

solution for u(x,h) as a functional depending on the original concentration u(x,o) and the growth curve, x(t) between the times t=o and t = nh.

21
The computation of Ax permits a new interpolation approximation to

x(t) between x(t + (n-l)h) and x(t + nh) . The interpolation maintains

both x(t) and x(t) continuous at all times. The new approximation for

x(t) between t = o and t = nh is cycled back into Subroutine 1 for a still better approximation to the growth curve. Cycling is continued un- til a stated degree of accuracy is reached. A perturbation argument

guarantees the convergence of this procedure for a finite time interval

beyond t = o. Whenever the concentration profile is desired or when it becomes

necessary to redetermine it for reasons of non-convergence of the hx.- iteration employed in Subroutine 1, Subroutine 2 is called to compute

a new profile uXx, t) and the iteration cycle begins anew. The expj'ess-

ion for this concentration profile given by the above-mentioned functional

is

x^ Cf j-t + ^w)

-/r;

o

^

Subroutine 3 is an integration procedure which records the truncation error for each integral. It is thus possible to control the

step size automatically in order to keep the total error below a prescribed bound.

The computer program for this procedure has been written and is

currently undergoing tests for its region of stability, the aim being

to allow the computation of x(t) on as coarse a grid t + nh as possible

in order to keep the computer use at a reasonable cost level.

22
3. DEFECT CHARACTERIZATION

This chapter is concerned with

studies of defect-sensitive

properties of single crystals.

3.1 Optical Properties, of "Pure" and Impure Crystals

R. F. Blunt,

Solid State Physics Section

The spectra of a number of systems have been measured, including

"pure" ammonium chloride, NH^Cl, and NH 4CI doped with nickel, with

cobalt, and with copper. Magnesium Fluoride, MgFg, has also been studied

containing x-ray- induced color centers. Particular attention has been

devoted to MgFa

.

X-ray irradiated "pure" MgFg (rutile structure) produces, at room

temperature, a strong band at ~ 250 nm (mp.) (see report by M. I. Cohen,

Section 3.2 of this Note). This band is easily bleached by 250 nm light,

thereby producing a strong ~ 370 nm band. The ~ 250 nm band is slightly

anisotropic, but the resulting bleaching appears completely independent

of the orientation of the bleaching light. The 370 nm absorption band

is markedly anisotropic, occurring only in E|

C

spectra. Excitation

with light of wavelengths of less than ~ 400 nm gives rise to two luminescent bands, one at 420 nm that occurs with Ej_C, and a band at ~ 550 nm

that is isotropic. The luminescence is pronounced only when the exciting

light has EJ_C.

Preliminary irradiation studies of samples at liquid-nitrogen temperature are currently in progress and so far have yielded weak thermoluminescence and evidence relatively weaker absorption bands than those

obtained for room temperature Irradiation. The absorption bands appear to

be quite stable at room temperature, but are completely removed on a 500 °C anneal.

3.2 Irradiation Studies

M. I. Cohen,

Solid State Physics Section

Work in connection with the study of color centers in crystals of

magnesium fluoride, MgF,, has continued. During this period, several

changes have been made in our equipment. A tungsten- target, high-output

tube has been installed, increasing dosage rate by approximately four

times. Arrangements have been made to irradiate crystals at low temperatures in an optical dewar that can then- be transferred to a Cary 14 spectrometer without change in sample temperature.

As previously reported, (In Technical Note 236, Section 3.19), 50kV

x-rays appear to be the most efficient radiation for production of color

centers in MgFg . A number of samples of differing orientations and from

different sources have been irradiated at varying dosage levels . Speci23
mens have also been irradiated and optically examined at 78°K. In

addition to X- irradiation, a sample has been irradiated with 200 kV

electrons (total exposure, 6 x 10®R) . The results of these experiments

are discussed by R. F. Blunt in Section 3.1 of this Note.

A sample of MgFg obtained from Semi-Elements, Inc. was irradiated

with 50 kV X rays for a total of three hours (total exposure, ~ 10 ''R) . The sample was examined at intervals during the irradiation. The

growth of the absorption band at 250 nm was found to be very rapid

during the initial hour of irradiation. The growth rate of the

absorption band then fell off rapidly with further irradiation.

3.3 Dislocation Studies in Metals

A. W. Ruff, Jr. and L. K. Ives,

Lattice Defects and Micros tructure Section

The variation of stacking-fault energy with composition is being

studied in a series of silver solid-solution alloys. The technique

involves measurements on extended dislocation nodes observed by

transmission-electron microscopy. Experiments involving silver alloys

in the composition range" - 8 a/o tin are in progress. Preliminary

results indicate that solute additions decrease the stacking-fault

energy from that of pure silver and that extensive twin formation is

observed at higher solute concentrations. The effects of compositional

inhomogeneities (segregation to the faulted regions) will be examined, together with the effects of size and valence of different solutes.

It is planned to compare the results with x-ray diffract ion- fault ingprobability measurements on the same alloy system. (see Section 3.4)

3.4 Stacking Fault Probabilities in Metals

C.J. Newton and A. W. Ruff, Jr.

Lattice Defects and Micros true tures Section

A study of stacking-fault probability by means of x-ray diffraction effects has been undertaken in a series of solver alloys. Small

relative changes in the separation of the diffraction peaks in the

x-ray powder pattern are observed when one compares the pattern

from the cold-worked material with that from annealed material of the same composition. This relative peak shift, as well as certain

other diffraction effects, enables one to calculate the probability

of faulting in the cold-worked material. The specimens examined at

present are carefully prepared from filings of the alloys; consideration is being given to measurements on solid-alloy specimens with

a fine grain structure. (see Section 3.3)

24
3.5 Thermodynamics of Segregation of Solute Atoms

to Stacking Faults in FCC Binary Alloys

R. deWit,

Lattice Defects and Micros true ture Section

and

R. E. Howard,

Metal Physics Section

Since the stacking- fault energy in many FCC (face-centered cubic)

metals is lowered by alloying, thermodynamic equilibrium requires that some segregation of solute atoms to the stacking faults takes place to

lower the total free energy. Instead of assuming with others that the

width of the extended dislocations remains fixed during the segregation, we suppose that the width always has the equilibrium value corresponding

to the local concentration at the stacking fault and thus changes continually. A further generalization that may be more realistic was also

made, which was not previously considered (see NBS Teclinical Note 236,

Section 2.3). Instead of maintaining mechanical equilibrium for the

extended dislocations, no such "a priori" assumption was made. Now, two

general conditions of thermodynamic equilibrium are found. The first

is the same as that derived previously without the above assumption by

Dorn and Suzuki; it gives the relation between the solute concentration

xf in the faulted region and X in the matrix if the stacking- fault en- ergy dependence on the local concentration is known, and can be interpreted as a Maxwell-Boltzmann distribution of the solute. The second

is a new expression for the stacking- fault width w in terms of the

stacking- fault energy and an entropic term, and can be interpreted in

terms of the balance of forces on each partial dislocation.

It is found that the locking stress, which is the resolved shear

stress required to free a dislocation from its segregated atmosphere,

is not changed by the above extension of the theory.

On the crude approximation that the stacking fault energy y is

exactly the difference in the free energy of the FCC and HCP (hexagonal

close-packed) structures of the same composition and temperature, it

is shown that the FCC and HCP phase boundary concentrations of the

alloy are found as a special case of the theory when the stacking fault

width approaches infinity. This shows again, contrary to Suzuki, that

the stacking fault width cannot increase indefinitely.

The stacking fault energy versus composition dependence for the

unsegregated alloy is given by the 7 versus xf curve; for the fully

segregated alloy this dependence is given by the 7 versus X curve. Both the 7 versus X and the w versus X curves are found from the 7 versus Xf curve by the two conditions of equilibrium. It is suggested

that work-hardening experiments may measure the 7 versus xf dependence,

dislocation node measurements the w versus X dependence, and x-ray

experiments the xf versus X dependence.

The present theory may have important applications to the measure- ment of the stacking- fault energy which is an important parameter in

theories of mechanical properties of materials

.

25
3.6 Characterization of Electrodeposited Crystals

F. Ogburn and A. de Koranyi,

Electroysis and Metal Deposition Section

Examination of electrodeposited lead dendrites, which are flat or 2-dimensional, shows them to be oriented with fill} planes parallel to

the plane of the dendrite. At least two orientations with a twist re- lation aboxat the common [111] pole are always present. The twist angles

observed were 20°, 27°, 30°, 33°, 37°, and 50°. For each dendrite, the

direction of growth was half way between a [211] direction of one orientation and a neighboring [211] direction of the other orientation.

Another phase of this project involves development of techniques

for growing copper dendrites by electrodeposition in such a size and

form that they may readily be used for other experiments. This empirical

study has been informative, but only partially successful in that con- trolled growth of a single dendrite has not been achieved. Several of

the dendrites, the dimensions of which are measured in millimeters and

centimeters, were examined metallographically . The twinned structure

reported in Technical Note 236, Section 3.10 was consistently observed.

Not infrequently, however, other structures were observed along with the

twin boundaries. It remains to be determined if this structure is inherent and what it is due to.

3.7 Defects in Thin Oxide Films

J. Kruger and C. L. Foley,

Corrosion Section

Thin-foil electron microscopy and diffraction were applied to a study of the films formed on iron during potentiostatic anodic polarization. The techniques consisted of anodically polarizing thinned ironfoils in boric acid-sodium borate solutions at various passive potentials.

By then flooding the surface, while it was at the passive potential

with an inert liquid it was possible to retain the electrochemically formed films so that they could be studied in the electron microscope. Selected-area transmission electron-diffraction studies of these foils

offered the advantage that one could study the epitaxial relationship

of the oxide with metal substrates of different orientation on a single

polycrystalline specimen.

These studies have shown that the films formed under the above described conditions are highly oriented, and have a spinel structure. The

major difference between the passive and non-passive films was found to

be the appearance of superlattice lines in the case of the passive films.

These lines are those predicted by Bloom for 7-Fe203 containing hydrogen

in vacant iron sites. This work (Kruger and Foley, 1964) will be presented before the Electrochemical Society in October.

26
3.8 Report on Nuclear Magnetic Acoustic Resonance

L. H. Bennett and R. W. Mebs

,

Alloys Physics Section

The interaction of the nuclear-electric- quadrupole moment with

crystal lattice-vibrations is the mechanism which makes possible the

detection of nuclear magnetic resonance in bulk materials by the acoustic

excitation method. This type of investigation suggests itself as being

particularly useful in the study of the nuclear magnetic resonance in

metals, since it permits the employment of single crystals instead of

finely divided metallic powders usually employed in conventional nuclear

magnetic resonance studies.

The crystals employed are those with limited numbers of structural

defects such as dislocations, vacancies and stacking faults, and it must

be possible to provide optically flat and parallel faces to each sample

without appreciably disturbing its defect structure. Inasmuch as the

metals selected must have a large quadrupole moment, the investigation

further lends itself to a study of the effect of its defect character,

as well as a quantitative measurement of the quadrupole interaction.

Furthermore, the influence of the orientation of the applied magneticfield with respect to the crystalline axes on the intensity of the

measured resonance can be studied inasmuch as some defects have a directional preference with relation to such axes

.

The present investigation is employing a nuclear-resonance spectrometer system consisting of an oscillator-detector-recorder assembly plus

an adjustable high- intensity precision electromagnet with a centrally

homogeneous field. Some additional matching circuitry is used with the

transducer-crystal probe, and has been used successfully in observing

nuclear-magnetic acoustic resonance in a potassium- iodide single crystal.

Additionally, high-purity copper and indium antimonide single

crystals have been secured, the latter possessing a fairly low carrier

concentration. Although suitable barium-titanate transducers have been

obtained for use with the copper sample, to date no reproducible

measurable resonance has been detected. There was a preliminary unsatisfactory attempt to measure resonance with the indium antimonide crystal

with attached quartz-crystal transducer. Subsequently, normal nuclear

magnetic-resonance measurements were made with the same spectrometer on

this crystal, with its axis being rotated with respect to the magnetic

field. No measurable variation of resonance amplitude with respect to

orientation could be detected. This might indicate either that the

crystal was quite free of defects, or that the deformation had extended

beyond the point where only preferential planes were involved. Hence,

the crystal was carefully strain-relief annealed in hydrogen and again

prepared for test.

A broad survey is being made of available single crystals of metals

possessing suitable quadrupole moments, both from industrial sources and

from our own single-crystal facilities. Such crystals necessarily must

be of high purity and possess a limited number of defects

.

27
3.9 Laser Microprobe for Analysis of

Very Small Samples

B. F. Scribner, M. Margoshes,

and

S. D. Rasberry,

Spectrochemical Analysis Section

A description of a laser microprobe source for analysis of small

samples was given in NBS Technical Note 197, Section 3.10. In the last

six months, experiments with this apparatus have been directed toward

improving the reproducibility of this source, and investigating the

character of sample vaporization by the laser and the sparking of this

vapor with cross -electrodes

.

Apparatus was designed to detect the laser-power output as a function of time, simultaneous with sample volatilization by the laser.

This direct observation of the laser permits immediate evaluation of

changes that variations in laser optics and pumping made in the laser

output, and size of pit produced on the specimen. Modifications were

made to bring the giant-pulse ruby laser into single-spike operation,

resulting in better reproducibility of laser operation, and sample

vaporization. The modifications required to achieve reproducible

single-spike operation were: Use of a more angle-selective from reflector, partial internal masking of the laser cavity, and lowering operating

temperatures by 25 °F and 80 °F . The difference in power output, as a function of time, between multiple-spike and single-spike operation is

illustrated in Figure 16. The variation of crater diameter with an increase in laser energy output for single-spike operation is illustrated

in Figure 17, where the sample is NBS Zn Base Standard 629.

The more consistent laser output available with the single-spike

laser pulse permits greater confidence in studies of other variations

in the system. The characteristics of sample excitation, as a function

of spark voltage, resistance, capacitance, inductance, and electrode

configuration have been determined in the case of varying these parameters singly. Results indicate that the intensity changes which accompany

variations in these source parameters differ between the laser microprobespark and conventional spark sources. This difference may be accountable

to the fact that in conventional spark sources the spark volatilizes as well as excites the sample.

28
B

Fig. 16. Recordings of power vs time for (a) mutliple=

spike laser output and (b) single spike laser

output. Two successive recordings are shown

for each case. Time scale; 200 nanoseconds=

1 large division.

60

50

40

Crater

Diameter

(in Microns)

30

20

110

Fig. 17

120 130 140 150

Crater diameter vs laser output.

NBS Zn base Standard 629.

Sample is

29
3.10 Accurate Measurement of the Fundamental

Electrical Properties of Semiconductor Crystals

J. C. French, L. J. Swartzendruber,

G. G. Harman, H. A. Schafft,

and

N. Winogradoff,

Electron Devices Section

Following the completion of the solution of a number of electrical

potential problems having application to two- and four-point probe

measurements, as described in NBS Technical Note 236, Section 3.12,

the remaining results were prepared for publication (Reber, 1964)

(Swartzendruber, 1964a, b, and c) . Some of this material will be a part

of the American Society for Testing and Materials Proposed Tentative

Method of Test for Silicon Radial Variation of Resistivity, which is now in draft form.

Attention turned to the experimental determination of the resistivity variation in silicon single-crystals. This variation appears to be

one of the limiting factors in the establishment of standard samples.

The best commercial sample received for evaluation varied in resistivity

(about a nominal value of 14 ohm cm) by ±47o over a diameter of 3.3 cm

and ±57o over a length of 2.5 cm. A neutron- irradiated sample of about

the same resistivity was not greatly superior to this. Unfortunately,

these variations are not monotonic functions of distance so that

correction for their effect is difficult. A cooperative program with

industry has been established with the aim of producing more uniform

material specifically for this purpose.

A thorough study of the accuracy attained to date in the resistivity measurements was completed. Measurements were made on both circular wafers and rectangular parallelopipid bars cut from the wafers,

using both two- and four-point probe techniques with two different

probe spacings. Appropriate allowance was made for anticipated errors arising from the effects of the many factors involved, such as sample

dimension variation, probe spacing variation and misplacement of the

probes, and temperature effects, after these factors had received

both experimental and theoretical analysis.

In the case of this 14 ohm-cm material, and on a single laboratory

basis, the various measurements were found to have one sigma (standard

deviation) limits of error of less than one-half percent, and the

various measurement: methods agreed to within this experimental error. Further work to improve these results is underway. It is expected

that the limit of error will be reduced in any event on the one ohm-cm

standard sample currently of greatest interest.

A new task has been undertaken in the study of second breakdown

in transistors* mentioned in NBS Technical Note 236, Section 3.12.

This is a cooperative effort with industry, concerned with determining

the importance to the development of second breakdown of strain, dislocations and other irregularities in the single-crystal semiconductor,

in the transistor. X-ray diffraction microscopy will be used to ob- serve these defects and a correlation of the defect sites with preferred

* This work was supported by the Rome Air Development Center.

30
locations of second breakdown will be sought in specially constructed

transistors

.

Work was started on a new program in which the recombination properties of hot carriers in silicon crystals will be studied. A literature survey and a band structure study were made, program ob;)ectives were established, and instrumentation was completed.

Some additional results have been published which have arisen

from the now concluded studies of muscovite mica (Ruthberg and Frankel,

1964).*

The solid-state technology project has continued to devote most of

its effort to work on silicon-crystal nuclear-particle detectors.

However, its sample preparation and analysis facilities have also con- tributed to the crystal characterization by diffraction topography

of R. D. Deslattes in locating material of suitable dislocation density, in preparing this material for x-ray analysis, and in correlation of chemical methods of dislocation density with x-ray methods.

Study of solid-state injection lasers began in the last weeks of

June, 1964.

3.11 Study of Crystal Defects

D. J. Barber and N. J. Tighe,

Physical Properties Section

The motion of dislocations in aluminum oxide at ~1500 °C has

been observed directly, using the high- temperature electron microscope

stage reported previously in NBS Technical Note 236, Section 3.4.

The results indicate that, at these temperatures, the passage of 100 kv

electrons through the sample produces point-defects. The defects

subsequently interact with dislocations, causing them to climb in a characteristic way, resulting in a zig-zagged appearance (Figure 18)

.

The hot stage has also been used to study phase transformation in

single crystals of quartz. During this work, the existence of ex- tended stacking faults on the [1011} planes has been revealed (Figure

19) . The faults are unaffected by the crans formation at 573 °C from

the a- to the P- quartz structure. Further study of the transformations is to be carried out using a cin^-camera.

* This work was supported in part by the General Services Administration.

31
%

'A a

'«>««*

Fig. 18. Stacking fault in (0001) section of a-quartz

prepared by chemical thinning.

0-5^^

Fig. 19. Climbing dislocations in a-Al^Oa under the influence

of a flux of point defects at ~1500°C.

32
3.12 Magnetic Resonance Studies

L. M. Matarrese, J. S. Wells, R. L. Peterson,

R. J. Mahler, and A. R. Cook,

Radio and Microwave Materials Section

The analysis of the EPR spectrum of ferric ion in quartz has been

completed. The work was reported at the APS meeting in Washington, and a paper is being prepared for publication. The values of the spin

Hamiltonian parameters that fit the data best are D (assumed positive) = 734, 1 G, E = 327.7 G, a^ = 37, 5 G, and g (isotropic) = 2.0043.

We plan to extend the investigation of iron-doped quartz to low

temperatures and zero field. (The zero-field splittings calculated

from the above parameters are approximately 6,6 and 8,5 GHz);see Figure

20, 21, and 22.

We believe that the ferric ions, are in substitutional sites, and

that a small positive ion, such as Na , Li , or H on the two- fold axis

and in the open optic-axis channel provides the charge compensation and

the strong axial field. ENDOR experiments are planned in an attempt to

check this hypothesis.

The EPR spectrum of amethyst has also been attributed to ferric

ion but is completely different from that of our iron-doped quartz

specimens

.

Another K-band h.PR spectrometer has been assembled for use in

AFMR experiments on the anhydrous sulfates of transition metals, which

have relatively low N^el temperatures . Preliminary experiments on powdered anhydrous CuSO^ show that there is still a paramagnetic reson- ance signal below the N^el point (34 °K) . This may be due to an impurity. We are now investigating single crystals of CuSO^

.

We have continued studies of the ultrasonic modulation of the magnetic interaction in antiferromagnetic KMnFg . Results have bean published in Physical Review Letters (Denis on, James, Curran, Tanttlia, and

Mahler, 1964) and will also be presented at the 13th Colloque Ampere.

Attempts to detect this effect in antiferromagentic CoCla«2H30 and

RbMnFg, and in paramagnetic LiF, ZnFg , and ruby met with failure. We

are now trying to observe a Raman phonon-doubling process in RbMnFg

and KMnF,

.

33
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36
3.13 Effect of Point Defects on the Dynamic

Properties of Crystals

J. B. Wachtman, Jr., S. Spinner,

and

S. Marzullo,

Physical Properties Section

Mechanical and electrical properties are being studied as a function of temperature and frequency and the results interpreted in terms

of chemical impurities and related point defects.

Previous work on vacuum reduced rutile (Wachtman and Doyle, 1964)

and on Ni-doped rutile has been extended both by combining the effects

of vacuum reduction and Ni doping and by Cr doping. Results appear to

be consistent with the idea that in all cases interstitial metal ions are present and that the measured activation energies are those for ionic

jumps between interstitial sites. In the case of Ni-doped rutile, two

peaks appear which have been attributed to paired and unpaired inters titials, respectively. This interpretation is supported by the '^observation

that the peak associated with pairs is still present after vacuum reduction, but the peak attributed to isolated Ni interstitials vanishes presumably because of association of these Ni ions with interstitial Ti ions

introduced by vacuum reduction.

Work on the dielectric loss peak associated with small amounts of

CaO in solid solution in ThOg has been continued. The size of this peak

increases with increasing CaO content up to one mole percent, but thereafter remains unchanged up to 10 mole percent, despite the fact that as much as 12.5 percent CaO will go into solid solution. The internal

friction peak associated with CaO in ThOg shows the same behavior.

3.14 Crystal Characterization by Double Crystal

X-ray Diffraction Topography

R. D. Deslattes and B. Paretzkin,

Crystal Chemistry Section

The work described previously (NBS Technical Note 236, Section

3.13) has been continued, especially on solution-grown ADP (NH^HaPO^).

With careful sample preparation and handling, specimens have been obtained whose topographs show neither local defect images nor significant

strain over regions exceeding 1 cm^ (Deslattes et al., 1964).

The perfection of these crystals together with the existence of

rather numerous strong, reflections provide a significant series of perfect

reference specimens with which this technique can be extended to many

other crystals.

Another application of these crystals is in high resolution x-ray

spectroscopy. Of the reflections so far studied, the following results

37
have been obtained in the double-crystal spectrometer at the wavelength

of CuK^ (1.54A).

Reflection Resolving Power (-t-t—) A A. 202 4.0 X 10*

220 4.5 X 10*

600 4.5 X 10^

The 220 reflection is of particular merit since it is unaccompanied

by other orders and has a percent reflection of 60.

3.15 Magnetic-Resonance Studies - I

T. Chang, R. A. Forman,

and

R. C. Frisch,

Solid State Physics Section

The work of this group can be broken into two main catagories,

nuclear magnetic resonance and electron paramagnetic resonance. Certain

materials are being investigated by both methods; for example, ammonium

chloride, NH^Cl, rutile, TiOg , and strontium titanate, SrTiOg, while

several others are specific to just one method.

(a) Electron-Spin Resonance

Electron paramagnetic resonance studies of transition metal- ion impurities in rutile are continuing. Earlier work on molybdenum, Mo^"*", in

rutile has been completed and work is in progress on tungsten, W^*, in

rutile. Both of these ions enter the rutile lattice substitutionally

and both have a d-"^ electron configuration in the valence states studied.

This is the first observation of tungsten as an impurity in a crystalline

lattice.

Since superhyperfine structure of the resonance line, which is the

effect of the interaction of the impurity electrons with neighboring

titanium nuclei, is observed for both Mo and W^"^ in rutile, a correlation of the two results was suggested. This correlation is possible be- cause both have similar (d^) electronic configurations and the same crystalline environment.

In addition to the above, work has begun on transition metal impurities in ammonium chloride and strontium titanate. Some work has also

been begun to aid in the identification of the color center (s) produced

by x-ray irradiation of MgF being studied by Blunt et al (see Section

3.1).

(b) Nuclear Resonance

The nuclear magnetic resonance study of potassium azide, KN3 , has

been completed and the quadrupole coupling-tensors for all nitrogen sites

in the crystal have been determined. The relatively small size of the

38
quadrupole coupling constants has necessitated the construction of new

apparatus for searching for the pure quadrupole resonance in other azides

where a nuclear magnetic resonance study is not feasible. Searches for resonances in sodium azide will be begun shortly.

Preliminary measurements have also been made on the N-"-* nuclear re- sonance in single crystals of ammonium chloride. A temperature dependence

study is currently in progress. Ammonium bromide and iodide will also be

investigated if large enough single-crystals can be grown.

Measurements of linewidths and chemical shifts of nitrous oxide,

NgO, nitric oxide, NO, nitrogen trioxide, NgOg, and nitrogen dioxide,

NOg , are also in progress. These measurements will be useful for estimating quadrupole effects to be expected for the nitrate and nitrite

ions in crystals. Single crystals of sodium nitrite, NaNOg , and sodium

nitrate, NaNOg, have been prepared, and searches are being conducted for

the nitrogen resonance in these materials.

Helium temperature investigators of rutile and strontium titanate

are planned. The quadrupole interactions of the titanium nucleus are presently unknown.

3.16 Automation of Single-Crystal X-Ray

Diffraction Intensity Measurements

F. A. Mauer,

Crystallography Section

Plans for the automation of an existing dif fractometer and singlecrystal orienter were discussed in NBS Technical Note 236, Section 3.14.

The prototype system has been assembled and is under test by the manufacturer. If its performance is satisfactory, the National Bureau of

Standards is to receive the first production models of the programming

and positioning modules. Installation is expected by January 1, 1965.

4. PHYSICAL PROPERTIES OF

CRYSTALLINE MATERIAL

This chapter is concerned with the

physical properties of crystalline

material where crystal perfection

is not a primary consideration.

4.1 Crystal Orientation Methods*

E. N. Farabaugh and P. R, Miller,

Crystal Chemistry Section

A study of the standard x-ray orientation procedures for single

* This work is partially supported by the Atomic Energy Commission

39
crystals has been undertaken to determine in what way these procedures

can be modified or refined to obtain the orientation of a crystal more

quickly and precisely. Laue back-reflection photographs and pseudoKossel line patterns are used in the program. The techniques developed

will be applied in support of other crystal research in which the

orientation of the individual crystal is a necessary part of the investigation.

4.2 Crystal Symmetry and Crystal Properties

J. B. Wachtman, Jr.,

Physical Properties Section

and

H. S. Peiser,

Crystal Chemistry Section

The application of stress to a crystal causes a lowering of symmetry in general with the result that atoms which originally had the same energy levels may become non-equivalent and have different energy

levels. This non- equivalence affects many properties such as internal

friction, optical spectra, electron spin resonance, etc., which are associated with the atom in question. Quantitative treatment of these

effects requiras a detailed theory for each, but selection rules can sometimes be derived from sjnmmetry considerations alone (compare NBS

Technical Note 236, Section 3.7). For this purpose, it would be useful

to have a tabulation of the possible patterns of non-equivalence which

can be set up by any possible stress for all types of positions in each

of the 230 crystallographic space groups. This large task can be some- what reduced by tabulating only the general position for each space

group because the special positions can then be derived easily. This

tabulation has now been completed for the centro-syrometric space groups

and work is in progress on the noncentro-symmetric space groups.

4.3 Studies in S olid-State Theory

A. H. Kahn,

Solid State Physics Section

A study of the electronic-energy bands of cuprous oxide has been

started. The tight-binding method is being applied in the same way as

in the recently completed study on strontium titanate, SrTiOg

.

Comparison with experimental transport and optical properties will

be made.

Published experimental infrared reflection data were analyzed to

obtain information about the long-wave length polar modes of lattice

vibration in rutile, TiOg . The continuum polarization model of electronphonon interactions was extended to apply to crystals with several types

of longitudinal polar phonons , and the results were used to discuss

polaron theory in rutile.

40
4.4 Electronic Transport

H. P. R. Frederikse, J. H. Becker, W. R. Hosier,

R. C. Keezer, D. E. Poland*, W. R. Thurber,

and

A. Mante**

Solid State Physics Section

Experimental determinations of the energy-band structure of strontium titanate, SrTiOs , (see NBS Technical Note 236, Section 4.4) are continuing through measurements of the Hall coefficient, electrical

conductivity, thermoelectric power, and recently the orientation dependence of magnetoresistance . Preliminary results on magnetoresistance

at 4.2 °K are consistent with the calculations previously made (Kahn and

Leyendecker, 1964). Studies will be extended to include piezoresistance.

Improvements have been made in the preparation of crystals with specific

electron concentrations (oxygen deficiencies) . These specially prepared

crystals are also being used in connection with research on superconducting semiconductors (see Research on Superconducting Semiconductors,

Section 4.21 of this Note).

In connection with the superconductivity and energy band structure

determinations, several other materials are being investigated. These

include BaTiOg , MoOg , Na WO3 , AuSbg , several II-VI and IV-VI compounds

(see Section 2.10) . ^ Facilities are being assembled and tested for studies of tunnelling

between metals and insulators (or semiconductors) which will yield

information concerning electron and phonon energy spectra.

The apparatus for studies of thermal conductivity at low temperatures has been improved and used in connection with studies of rutile.

Umklapp processes determine the temperature dependence of the thermal

conductivity in the range 25-300 °K. The value in the £ direction is

1.5 times that in an a direction above 15 °K. These samples of pure

TiOg have now been reduced to determine the effect of lattice defects

on the thermal conductivity.

4.5 Optical Constants of Materials from

1 to 1000 Rydbergs

R. E. LaVilla and R. S. Deslattes,

Crystal Chemistry Section

This is a new project whose objects are (a) to extend and improve

knowledge of optical constants of materials, (b) to extend the techniques of good crystal spectroscopy into the region where it overlaps

* NAS-NRS Research Associate

** NATO Fellow

41
with good ruled grating spectroscopy and (c) to undertake on the little

understood and presently controversial subject of the extended finestructure in the x-ray absorption-edge spectra of materials. This

would involve studies from 1 to 1000 Rydbers (X = lOOOl to lA)

.

The numerical procedures have been tested for extending and improving the data in the spectral region up to 3 Rydbergs . We plan to extend

these techniques to shorter wavelengths. Also, we will procure and

assemble a single-crystal vacuum spectrometer for absorption measurements in the 20 - 200A range on extremely pure materials

.

4.6 Hall-Effect Measurements*

S. Rubin,

Engineering Electronics Section

The objective of this project, as indicated in NBS Technical Note

236, Section 4.5, is the establishment of standardized terminology and

measuring methods for galvanomagnetic (Hall effect and magnetoresistive) devices

.

The results of the work of this project on sensitivity indices for

Hall generators have been published (Rubin and Rogers, 1964) and, in

addition, two other papers have been issued which present a tutorial

introduction to galvanomagnetic effects and describe proposed standards

for Hall generators (Rubin, 1964)

.

Work on standards of terminology and measuring methods for magnetoresistors and galvanomagnetic multipliers is continuing, and it is

anticipated that proposed standards in these areas will be available

by the middle of calendar year 1965.

4.7 Dielectric and Mechanical Properties**

J. H. Wasilik,

Solid State Physics Section

We have applied the Nath, Born-Smith de Launay theory for diamond

lattices [de Launay, Solid State Physics, 2, 219 (1956)] to several

* This work was supported by the Bureau of Naval Weapons

** This work was supported by the Atomic Energy Commission

42
zinc-blende structures. By a simple modification, we have reduced the

number of independent atomic-force constants from three to two, while

still retaining interaction out to next-nearest neighbors. Assuming the

interaction energies of the ions are describable by a Born-Mayer potential, V = - Ae/4 + B exp (-r/p) , we show that the next-nearest

neighbor, central-force force constant (de Launay's a^) is equal to the

nearest-neighbor, central-force force constant (de Launay's a;^ ) times

(nearest-neighbor distance/next-nearest-neighbor distance)'. This re- duction of the number of independent force constants results in a relationship among the three elastic constants which can be conveniently

expressed as C^^ = f(C;L^, C^g). The calculated values of C44 are given

in Column 2 of Table 1, and are compared with the experimental values,

Colmn 3.

Using an expression given by de Launay (op. cit. p, 294) and our relationship between a^ and a^ , we have calculated the transverse

optical mode frequencies. Column 4; the experimental values are given

in Column 5. In this calculation our relationship is not a necessity,

but it simplifies the computation and constitutes a further test for our assumption.

Also, using a straightforward Clausius-Mosotti, Lorenz-Lorentz

approach, we have obtained the lattice polarizability which is equated

to an effective charge/atomic-force constant, the same atomic-force

constant being used as in the transverse-optical-mode calculation.

We than calculate the effective lattice charge using as input data the

high-and low-frequency dielectric constants and the elastic constants.

The results are given in Column 6 of the table and are compared with

other results in the literature. Columns 7, 8, and 9.

TABLE I

1 2 3 4 5 6 7 8 9

C44 C44 uuTO ujTO e* e* e* e*

Material calc

.

exptl. calc

.

Pic us calc

.

Picus Whelan Fan

xlO^ • dynes /cm^ xlQi^ sec"^ et al. in Hannay

InSb 3.034 3.018 3.11 3.28 .332 .34 .34 .34

GaSb 4.56 4.325 4.18 4.25 .267 .30 .18

AlSb 4.38 4.15 5.87 5.92

InAs 3.77 3.959 3.74 3.95

GaAs 6.16 5.94 5.09 5.04 .418 .43 .46

CdTe 1.56 1.994

4,8 Electron-Spin Resonance of

Trans it ion -Metal Complex

H. C. Allen, Jr. and G. F. Kokoszka,

Inorganic Materials Division

The electron-paramagnetic-resonance of monomeric cupric ions in

zinc-doped copper acetate monohydrate has been observed at 77 °C, using

43
an X-band spectrometer. Single crystals containing less than 17o zinc

ions were grown from a slightly acidic aqueous solution containing

about 757o copper acetate and 257o zinc acetate.

The experimental results could be fitted to the spin Hamiltonian

H„=gpHS +gPHS +gpHS +ASI +ASI +ASI. The S- ^-zT z z ^1^ X X ^y*^ yy zzz xxx Y Y Y

values A = 0.0147 ± .006cm"^, A < O.OOlScm"^, and A < .0023cm~i were

z ' X y measured for the monomeric cupric ions. The g values were found to be

g^ = 2.344 ± 0.005, g = 2.052 ± 0.007, and g = 2.032 ±0.007.

These results are consistent with a model proposed by Slichter

[Phys . Rev., 9_9, 479 (1955)] in which he has shown that the components

of the hyperfine tensor should be twice as large for a monomeric species

as compared to the dimeric species when the exchange integral, J, is

much larger than the components of the hyperfine tensor. The g values

are expected to be the same for the monomeric and dimeric species. A

comparison of our results with the results of Bleaney and Bowers [Proc

.

Roy. Soc. (London) A214 . 451 (1952)] and Abe and Shimudu [Phys. Rev.,

90 , 316 (1953) ] shows a satisfactory agreement of experiment and

theory

.

Recently, we have reported on the electron-spin-resonance of some

tris couples of copper [Allen, Kokoszka, and Inskeep, (1963)]. The

magnetic parameters were obtained from polycrystalline samples of the

copper complex in the corresponding zinc matrix. It now has been

possible to grow single crystals of the tris coordination compound of

Zn'*"^ with 1-10 phenanthroline containing a small amount of the cor- responding^ cupric complex. The magnetic parameters obtained from the

single-crystal studies at liquid-nitrogen temperature are g = 2.273±

0.007, g = 2.064 ± 0.008, A = 160 ± 3 x 10"*cm~^. At temperatures

greater than about 60 °C , the signal was symmetrical with g = 2.13

±.01.

The coupling of the unpaired electron with the nitrogen ligands

has been measured at liquid-nitrogen temperature. Using this information, we have estimated the ratio of the effective fractional unpaired

spin density in a nitrogen p orbital with respect to the s orbital.

This ratio was found to be about 2:1. Thus, sp^ hybridization for the

nitrogen ligands seems' to be a good approximation.

4.9 Magnetic Properties of Salt Single

Crystals at Low Temperatures

B. W. Mangum and R. P. Hudson,

Heat Division

Magnetic susceptibility measurements have been made on a number

of rare-earth trichlorides at liquid-helium temperature and below.

The results were surprising and substantially different from the known

behavior of gadolinium chloride, GdClg, which exhibits a ferromagnetic

transition at 2.2 °K.

We have studied cerium chloride, CeClg, praseodymium chloride,

PrClg , neodymium chloride NdClg, and samarium chloride, SmClg, all of

-44
which appear to become antiferromagnetic; except for NdClg , however,

the evidence is suggestive rather than definitive. In NdClg , the

susceptibility between 0.1 °K and 0.9 °K increased with increasing

temperature and above 1.8 °K, the reverse was true. Between these

regions there are two anomalous, extremely narrow spikes, one at 1.03 °K

and the other at 1.75 °K. These spikes are extremely sensitive to an external applied d.c. field; a field of 50 oersteds almost completely

eliminates them.

In CeClg we have found a single spike at 0.350 °K below which the

susceptibility appears to be constant down to . 1 °K. Above 0.6 °K a Curie Weiss law is obeyed with a Weiss constant of 0.125 °K.

The susceptibility of PrClg does not even approximate a Curie

law in the liquid helium region, the deviation being "antiferromagnetic",

A Weiss constant of approximately 1 °K describes the data. Below

1 °K the susceptibility increases slowly with decreasing temperature

down to 0.3 °K and displays no spikes.

We have been unable to grow single crysts of SmClg . However,

due to the fact that the g-values are almost isotropic, we felt justified in studying a polycrystalline sample. Preliminary data obey

the Curie law down to 1.7 °K and show an "antiferromagnetic" departure

below this point.

4.10 Spin-Wave Study Using Single Crystals

A. S. Risley and H. E. Bussey,

Radio and Microwave Materials Section

Degenerate spin-wave coupling as a loss mechanism in ferrimagnetlc resonance of polycrystalline ferrite has been studied by a new method,

that of tilting a spheroid in the magnetic field (Risley and Bussey,

1964) . The necessary theory for measuring ferrimagnetlc loss by tilting of single-crystal ferrite and garnet spheroids has begun. Also, some experimental work was done on x-ray orientation.

4.11 Reference Data on Single-Crystal

Elastic Constants

J. B. Wachtman, Jr., S. Spinner,

and

R. W. Dickson,

Physical Properties Section

Elastic constants of inorganic single crystals are being determined

as a basic physical property when suitable single crystals become

available. The elastic constants of thorium dioxide, ThOg , at 25 "C were determined in collaboration with P. Macedo and W. Capps of the

Glass Section (Macedo, Capps, and Wachtman, 1964). The values of four

of the elastic constants of TiOg have been determined over the range

room temperature to 1000 °C (Spinner and Wachtman, 1964).

45
4.12 Deformation and Fracture of Ionic Crystals

S. Weiderhorn,

Physical Properties Section

The fracture surface energy of soda-lime glass is being studied

as a preliminary step to making such measurements on non-cleavable

ionic crystals. The double-cantilever cleavage technique as devised by

Oilman [J. Appl, Phys . , 31, 2208 (I960)] and by Westwood and Hitch

[J. Appl. Phys . , 3A, 3085 (1963)] has been used to obtain fracture en- ergy values of approximately 3370 dynes /cm in liquid nitrogen, 3410

dynes /cm in toluene-solid carbon dioxide, and 2920 dynes /cm in dry

nitrogen gas.

Crack motion was observed during the experiment using a 20X microscope. Fracture in all test media occurred in two stages, an initial

stage in which the crack velocity remained fairly constant at a value

less that 10~*cm/sec and a catastrophic stage in which the crack velocity was greater than 10 "^ cm/sec and was increasing rapidly. The

transition between the two stages occurred rapidly. The initial stage

of fracture was greatly dependent on the amount of water vapor present

at the crack tip and is believed to be caused by static fatigue in the

glass as described by Charles [Prog, in Ceram. Sci. , J., edt. J. E. Burke,

Pergamon Press, New York (1961)] and by Charles and Hillig [Symposium

on the Mechanical Strength of Glass and Ways of Improving It , Union

Scientifique Continentale du Verre (1961) ]. In liquid nitrogen , on ly

slight motion occurred before catastrophic failure. In air, 1.57c. water vapor, the crack growth preceding catastrophic failure was ex- tensive and was visible to the naked eye. If the initial stage of fracture was in fact due to static fatigue, then it is of interest to note

that static fatigue does occur in soda-lime glass at the temperature

of liquid nitrogen. The second stage of fracture is believed to be

dynamically controlled in the manner described by Berry [J. Mech. Phys.

Solids, 8, 194 (I960)].

Further experimentation is planned on glass. It is our intention

to extend the measurements to liquid helium temperature and to study

the effect of glass composition and surrounding media on the fracture

energy of glass

.

4.13 Nuclear Magnetic Resonance Studies in

Yttrium-Iron Garnets

R . L . S treever

,

Magnetic Measurements Section

Using nuclear magnetic resonance techniques, the magnetic

characterization of mixed crystals of yttrium iron gallium garnets

have been studied as the ferromagnetic iron atoms are replaced by the

"non-magnetic" gallium atoms . In addition to measuring the magnetic

fields at the nucleus of the ^"^Fe in these materials, which was the

primary objective of the work, we have also been successful in observing the nuclear resonance of ®®Ga and ''^Ga in these same samples.

These latter results are particularly interesting because gallium is a diamagnetic atom and the hyperfine field at the gallium site arises

through a transfer of the spin density from the neighboring oxygen

46
atoms, which are in turn polarized by their neighboring iron atoms.

Thus, the hyperfine interaction at the gallium is associated with the

superexchange interactions between the gallium and the iron.

A study of the concentration dependence of the hyperfine field has

allowed us to separate out the sign and magnitude of the contributions

of the hyperfine field from iron in both (a) and (d) lattice sites.

Thus, we have been able to obtain an estimate of the relative magnitude

of the a-d and the d-d interactions in these materials. The ^Te

studies have also unabled us to estimate the relative number of gallium

ions which substitute on to (a) and (d) sites in these materials. This was one of the primary objectives of the work.

From the ^'Fe nuclear resonance studied, we have obtatined information regarding sublattice magnetizations in these materials as a function of gallium concentration. A paper covering this work (Streever

and Uriano, 1964) has been published. Another more detailed paper is

being prepared and will be submitted for publication in the near future.

Future plans involve further studies of these resonances in single

crystals of these materials, together with studies of other rare-earth

garnets

.

4.14 Metal-Oxide Melting Point Standards

S. J. Schneider,

Crystallography Section

Reactions between metal-oxides and suitable container materials

such as Ir and W are being investigated to determine possible inf lu 'nee

of container materials on the melting behavior of standards (NBS Technical Note 236, Section 4.10).

The NdgOg-Ir system was the first of a series studied in detail.

All experiments were carried out in air inasmuch as Ir has been chosen

as the container material for many of the melting point determinations

involving an oxidizing environment. The results showed that under

equilibrium conditions Ir first oxidizes to IrOg and then reacts with

NdgOg to form binary compounds. The NdgOg - IrOg system in air contains two compounds, SNdgOg'ZIrOg and NdgOg • 2Ir03 . The former is of

unknown symmetry while the latter was identified as a cubic pyrochloretype compound.

At temperatures above 1300 °C, each of these compounds dissociated

to the original mixture of NdsO, and Ir . Additional heat treatment of

the various speciments to 2000 C indicated that further reactions did

not take place in the solid state.

4.15 Soft X-ray Spectroscopy

R. D. Deslattes,

Crystal Chemistry Section

The unavailability of good potassium acid phthalate crystals has

continued (NBS Technical Note 236, Section 4.22 and this Note, Section

2.8). This has prevented investigation of the neon K spectrum and

47
those of sodium and fluorine in NaF (NBS Technical Note 197, Section

3.7). However, the planned automation of the instrument was completed.

Attempts to look with secondary excitation at the ^valence spectra

of III - V compounds and their group IV analogs near 8A have given

very low intensities. It seems that adequate delineation of these

profiles requires either a vastly more powerful primary radiation source

(possible of the order of 40 kw to generate 1 spectrum per week of

continuous operation) or a facility for direct excitation under sanitary conditions. The latter alternative seems more easily realizable

and more economical. Preliminary designs are therefore in progress.

Meanwhile, a re- exploration of the krypton L spectrum has begun

with special attention to effects of configuration interaction and

multiple excitation. These effects naturally occur also in the spectra

of crystalline materials where they add to the confusion in sorting

out the specifically solid state aspects of these spectra.

4.16 Crystals of Organic Molecules

R. A. Keller and D. E. Breen,

Physical Chemistry Division

Measurements of the extinction coefficient for triplet-triplet

transitions in some aromatic hydrocarbons have been completed. The

results are given below.

Compound Wavelength Extinction Coefficient

naphthalene-he 4140 A (1.6±0.3) x 10* liter /mole cm. naphthalene-dg 4140 A (1.4±0.3) x 10* liter /mole cm. phenanthrene 4925 I (2.7±0.5) x 10* liter /mole cm. triphenylene 4300 A (0.7±0.2) x 10* liter /mole cm.

These results will be submitted for publication in the near future.

Preliminary measurements have been made on the intramolecular

transfer of excitation energy between two isolated chromophors on the same molecule. Work on this project is still in progress.

Some progress has been made on understanding the nature of the

interactions involved in intermolecular interactions between two

excited triplet molecules. These interactions result in non-radiative

deactivation of the triplet state and also give rise to delayed flu- orescence.

48
4.17 Experimental Determination of

Atomic Scattering Factors

G. Bur ley.

Crystallography Section

This is a new pro5ect, designed to accurately determine selected

atomic scattering factor curves and compare these experimental results

with the tabulated theoretical values. The atomic scattering factors

for magnesium and oxygen in MgO have now been determined and the

results may be summarized as follows:

1) Both atoms exist as divalent ions in this structure.

The scattering factor curve for the oxygen agrees

almost perfectly with that calculated for the 0~^

anion

.

2) The scattering factor curve for the magnesium ion

deviates considerably from the Hartree-Fock selfconsistent field derived value. The experimental

values are lower to a sin9/\ value of about 0.50A~^

and then merge with the theoretical result.

3) At temperatures above 25 °C the difference between

the theoretical and experimental results for magnesium gradually decreases, until at about 600 C

the two curves become identical. This may indicate

a closer approach to spherical symmetry at elevated

temperatures

.

4.18 Velocity of Sound in Ice Single Crystals*

T. M, Proctor,

Sound Section

The search for a low- temperature vibrational mode in single

crystals of ice (NBS Technical Note 197, Section 4,1) is continuing.

The determination of the elastic constants from velocity of sound

measurements requires that the direction of the acoustic particle

motion be known with respect to the crystallographic axes. Ice

crystals present a number of environmental problems with regards to

the formation and measurement of specific crystallographic orientation,

Among these are the facts that ice is not dimens ionally stable at

normal temperatures, humidities, and pressures and that it cannot be

machined at temperatures above -40 °C

.

Efforts to get around the pressure sensitive freezing point

characteristic of ice have led away from the machining operation as

a means of sample forming. Instead, crystal samples are grown between two parallel plastic plates. Not only can the shape of the

sample be determined this way, but the crystal orientation can be

set by the use of a seed crystal. The seed is installed between the

plates in such a fashion as to give the desired crystal orientation.

* This work is partially supported by the Office of Naval Research

49
A special rig is used to position and hold the seed while the growth

is carried on. A certain amount of repeat growth is necessary in

order to converge on the desired crystal orientation.

With transparent crystals, measurement of crystal orientation

is accomplished by standard optical means. This method consists of

shining highly convergent polarized light through the crystal. Through

the analyzer, a typical interference pattern is seen along the direction

of the c-axis for a uniaxial crystal like ice.

For ice, the additional problem of making these orientation

measurements under a special environment of very low humidity and of

temperature below -10 °C exists. An apparatus for this purpose has

been constructed and has been used successfully.

An elaborate step-by-step routine is followed in order to keep

the dimensions of the sample constant. Several measurements (c-axis

orientation, sample thickness, velocity of sound) must be made on one sample. Dimensional changes from condensation, sublimation, and from

pressure and temperature melting must be guarded against. The

sample's surfaces are kept covered by the plastic plates in which they are grown during the c-axis orientation measurement. The samples

thickness must be measured at temperatures of -40 °C or lower and in a very dry atmosphere. The whole experiment must be performed quickly so as to minimize the sublimation problem.

4.19 Density Measurements

H. A. Bowman and R. M. Schoonover,

Mass and Volume Section

The Cartesian Diver System is being developed for water-weighing of objects too small for reliable observation on ordinary hydrostatic balances. Such balances of conventional design have un- certainties of 20 micrograms or more; hence, their percentage precision for very small objects is severely limited. Unfortunely,

objects of greatest interest in hydrostatic weighing (highly purified substances, single crystals, sensitivity weights, etc.) are not readily available in large sizes. Basically, density determinations are being made by attaching an object to the outside of the

Diver and measuring the pressure in the water that will result in zero vertical movement of the Diver. Work to date has consisted of

apparatus, and experiments with diver bodies of various hydrodynamic

shapes

.

At the present state of Diver art, hydrostatic weighings can be

made reproducibly to a standard deviation of one or two micrograms.

Experiments are conducted on one-gram objects occupying a volume of

about 1/20 cm^ . This precision is comparable to that obtained in a high quality air weighing. Efforts at present are being devoted to

obtaining volume trically stable objects which can be used as com- parison standards in Diver weighings. Experiments are being conducted on nichrome and gold, with platinum, fuxed quartz and pyrex to

follow shortly. As soon as stable standards are developed and calibrated against mercury, they will be compared hydros tatically with

various single crystals, probably beginning with rutile.

50
The density of near perfect single crystals is an important

parameter in the crystal characterization program, because, in some

cases, lattice defects and impurities are most easily detectably by

density differences.

4.20 Superconductivity in Niobium

V. D. Arp,

Cryogenic Properties of Solids Section

Fermi-surface properties of niobium are responsible for ideal

class II super-conducting properties of the highly purified metal.

Measurements of the anomalous skin effect and magnetoresistance are under way to provide more detailed information on certain of these

relations

.

In the process, we have annealed commerically available niobium

to achieve a resistance ratio (Roqq °v/^a °v^ °f 300 in a polycrystalline

sample. Results of measurements are expected later this year.

4.21 Research on Superconducting Semiconductors

J. Schooley and E. Ambler

Cryogenic Physics Section

and

W. R. Hosier and J. H. Becker

Solid State Physics Section

The discovery of superconductivity in the semiconductor strontium

titanate, SrTiOg , by measurements below 1 °K of electrical resistivity

and magnetic susceptibility (Schooley, Hosier, and Cohen, 1964) has

taken place through the cooperative efforts of the Cryogenic Physics

and Solid State Physics Sections. This resulted from the unique lowtemperature facilities and techniques, and extensive energy-band

studies on SrTiOg , (see Technical Note 236; Frederikse, Thurber, and

Hosier, 1964); (Kahn and Leyendecker, 1964 and Kahn , Frederikse, and

Becker, 1963) coupled with recent applications of the BCS theory

[Bardeen, Cooper, and Schrieffer, Phys . Rev. 108 , 1175 (1957)] of

superconductivity to multivally semiconductors (^Cohen, Phys. Rev. 134 , A511, 1964). The importance of this subject lies in the ease of testing

theories of superconductivity, and possible technological applications

which may result from the extended knowledge.

Studies on SrTiOg are continuing. Preliminary data of four-terminal resistance indicate that the superconducting transition temperature

T (defines here as the temperature for which R/R y a-\ = 0.5) depends

on electron concentration n approximately as: "°

T^ (H^) °K = 0.7 exp(-3.07 x 10^ n -^^^)

for n ~ 10 ^^ to 3 X 10^ ^/cc with a maximum in T of ~ 0.3 °K occurring

for n between 5 x 10^^ and lO^o/cc. ^

A wide variety of other materials is also being studied. The select51
ion of these is based on theoretical principles and limited information

of physical properties available in the literature.

4.22 Optical Properties of Cadmium Sulfide

and Telluride*

L. H. Grabner and R. C. Keezer,

Solid State Physics Section

Investigation of the quenching of photoconductivity of CdS near

the absorption edge is nearing completion. In addition to the experimental facts summarized in Technical Note 236, Section 3.18, photoconductivity peaks have been identified as due to excitation of free

excitons from the three valence bands of CdS. These are observed at

temperatures as high as room temperature and permit a determination of

the bandgap as a function of temperature to three significant figures.

The mechanism of quenching previously thought to be due to the shortening of the lifetime of a bound exciton by induced emission may have

to be modified by our inability thus far to detect the quenching at

temperatures of 10 °K. Acceptor levels close to the conduction band

may be responsible. A defect of this kind has been observed by

M. R. Lorenz and H. H. Woodbury [Phys . Rev. Letters, J^, 215 (1963)]

in CdS and CdTe by transport measurements

.

4.23 Soft X-ray Spectroscopy of Metals and Alloys

J. R. Cuthill and M. L. Williams

Alloy Physics Section

A 2-meter, grazing incidence, soft X-ray spectrometer employing a 30,000 lines/inch grating and a Bendix strip multiplier detector has

been built. The instrument covers the spectral region of 25 to 800A

and will be employed to observe the characteristic X-ray spectra cor- responding to transitions from the valence band to the outermost

normally filled level. The distribution of occupied states in the valence band is related to this spectra through the transition probability

coefficients involved. Of particular interest in the NBS program is the

study of change in the dens ity-of-state distribution upon the formation

of congruent melting, intermetallic compounds. Single crystal specimens

will be included and the effect of cold working will be studied.

This work was supported by the Office of Naval Research.

52
5. CRYSTAL CHEMISTRY

This chapter is concerned with

studies of crystal structure,

phase relations, and other chemical properties not sensitive to

crystal perfection.

5.1 Standard X-ray Diffraction Powder Patterns*

H. E. Swans on,

Crystallography Section

Diffraction patterns are produced in a continuing program for the

Powder Data File, a reference compilation for identification of crystalline materials . The NBS patterns have been published in thirteen volumes

as Circular 539 and Monograph 25. The latest issue (Swanson, Morris,

Evans, and Ulmer, 1964) includes primarily, inorganic compounds. For

materials with simple structure and which are different to obtain,

calculated patterns are now being prepared.

Improved reliability in cell dimension is now being sought for

internal standards of silver, tungsten, and cadmium oxide through care- fully controlled measurements of several samples

.

5.2 Apparatus for High-Temperature Preparation

of Pure Crystalline Polymorphs

A. R. Glasgow, Jr.,

Analysis and Purification Section

A special cell was designed for use to 1000 °C in phase purifications and thermal analysis for the purification of 20 -40g amounts of

pure polymorphic crystalline forms of BeFg

.

Three metals are used in the fabrication; inconel to withstand

oxidation at high temperatures, nickel to withstand fluorides at high

temperatures, and monel to resist attack by both oxygen and fluorides

at lower temperatures . Access to the cell is through a high-vacuum

coupling of monel at the top, which contains an opening for evacuation

and pressure control. One part of the coupling is welded to the double

walls of inconel and nickel comprising the shell and the other to the

double walls comprising a re-entrant coolant well. Thus, the inner

system is all nickel and the outer - all inconel in the potions subjected to high temperatures. The cell is provided with removable nickel

vessels at the bottom, lower-center, and top, in which the products

as solids can be removed after phase separations involving distillation, preferential decompositions, sublimation, and crystallization.

* This work is partially supported by the Joint Committee on Chemical

Analysis by X-Ray Diffraction under the auspices of the American

Society for Testing and Materials, The American Crystallographic Association, The British Institute of Physics, and the National Association

of Corrosion Engineers,

53
The operations are performed with the cell placed in a vertical position

in a three-zone control furnace. For thermal analysis, two thermocouples are located in the well and two at the bottom of the cell.

Careful attention was given in the design of the cell to details

of simplicity, chemical inertness, thermal expansion, mechanical

strength, measurement, and control of temperature and temperature gradients, and flexibility in operation. As a result, with the new equipment, much higher temperatures (up to 1000 °C) and much more favorable

conditions for thermal analysis for the detection of polymorph formation

should be available. This cell was completed by our shops on July 7,

1964, and is now being put into service.

5.3 Fermi Resonance in Solids

S. Abramowitz and J. J. Comeford,

Heat Division

The infrared absorption spectra of CF4 and CCl^ have been observed

in both pure form and in rare gas matrices at low temperatures . The

region studied corresponded to the V3 , 2v4 , and vs ^ vi + V4 Fermi

doublets of CF^ and CCL^ , respectively. The interactions of the vibrations involved in the resonance in these molecules changes considerably from that found in the gas phase. The results are consistent with

recent theories

.

5.4 Crystal Structure Analysis

S. Block, H. M. Ondik, A. Perloff,

and

L. H. Hall,

Crystallography Section

The structure of SrB^O, which was recently completed has revealed

an unusual borate network. All the boron atoms are tetrahedrally

coordinated. Furthermore, one oxygen atom is coordinated to 3 boron

atoms. The projection of the struture on the ab plane is shown in

Figure 23. The numbers indicate fractional z coordinates. The unique

oxygen is at z = .22. This structure, when compared with that of

BaB^O,;, shown in Figure 24, indicates that the coordination of boron

cannot be simply correlated with composition. Although BaB^O, has

the same boron-oxygen content as the strontium compound, half of the

boron is triangularly coordinated by oxygen, while the other half is

tetrahedrally coordinated.

Other work includes the first complete structure determination of

a halogenated boron hydride (iodopentaborane) . The investigation was carried out at -25 °C and showed, in agreement with NMR spectra, that

the iodine is bonded to the apical boron.

Complete 3 dimensional data for bis-carborane has been collected

with a counter diffractometer and CuK^ radiation. It is hoped that a new method will be useful for computing the structure.

54
Sr B

O O

Fig. 23. Projection of structure of SrB^O-, on the ab plane.

Fig. 24. Projection of structure of BaB^O^ on the ac plane,

55
Single crystals of the low temperature form of LigPO^ have been

grown and the structural relationship of the high and low temperature

forms is being investigated by single crystal techniques.

The determination of the structure of the triclinic form of

sodium tetrametaphosphate tetrahydrate (Ondik, 1964a) showed that its

relationship with the monoclinic form was that of packing. Both forms

have similar phosphate rings.

The structures of the pair, NagPaOg and NagPaOg 'HgO, were determined and revealed the interesting phenomena of a hole occurring in the

anhydrous form. This hole is filled by the water molecule in the

hydrate (Ondik, 1964b)

.

5.5 Crystal Chemistry of Mineralized Tissue

W. E. Brown and E. C. Moreno,

Dental Research Section

It is well accepted that the principal inorganic constituent in

tooth and bone is hydroxyapatite . Its unique structural relationship

to hydroxyapatite has introduced the possibility that octacalcium

phosphate is of great significance in physiological systems. We have

proposed that its role is largely a transitory one, but by participating in the formation of the crystallites of tooth and bone it contributes

materially to their chemical and physical properties. Octacalcium

phosphate appears to participate in the growth processes in at least

two important ways

.

1. It provides the seed or nucleus on which the hydroxyapatite

is later deposited. In enamel, this seed is a ribbon, possibly of

unit-cell thickness, of octacalcium phosphate. In bone and other

precipitates, it is thought that the same nuclei are present but in much

less elongated form. ,

2. Subsequent growth of apatitic crystals may take place through

a two-step mechanism requiring alternately the laying down of a unitcell thickness of octacalcium phosphate followed by its hydrolysis to

a twq unit-cell thickness of hydroxyapatite.

5.6 Phase Equilibria

E. M. Levin and R. S. Roth,

Crystallography Section

In a continuation of studies on the polymorphism of BigOg

(Levin and Roth, 1964), the heats of transformation of BigOg were determined by differential thermal analysis. The values obtained were:

BigOg transition (monoclinic <^730°G^cubic) - 9.9 kcal/mol and BigOg

fusion (cubic.^S25_Il_^ liquid) - 3.95 kcal/mol. A value of 2.05 kcal/mol

for the heat of fusion was obtained earlier [E . M. Levin and C. L.

McDaniel, J. Am. Ceram, Soc, 45, 355 (1962)] from the slope of the

liquidus curve in the BigOa-BgOa diagram.

56
Solid state studies in the system Nb^Og-TiOg (Waring and Roth,

1964) have lead to the discovery of a series of tetragonal phases of

the general type lOMgO^ • 9OM2O5 where M is P, As, Ge, or V and M' is

Nb or Ta. These phases are apparently isostructural with TagOg • 2NbgOB

.

The compound FeNbO^ has been found to be trimorphic (Roth and Waring, 1964) . The low temperature (monoclinic) form transforms at about

1085 °C to an orthorhombic ixiolite type which, in turn, transforms to a third form at 1475 °C which is isostructural with rutile.

5.7 Radial Distribution Studies of Glasses

S. Block, A. Hyman, and G. Piermarini,

Crystallography Section

Radial distribution studies on vitreous and crystalline borates

(NBS Technical Note 236, Section 5.11) have been continued. An analysis of radial distribution curves obtained earlier (Piermarini and

Block, 1963) [Block, Molin, and Piermarini, J. Am. Ceram. Soc, 46, 557

(1963) ] shows that a model based on random packing of hard spheres

cannot adequately account for the shape of these curves. The modifieroxide cations must be assumed to occupy positions which show some degree of order. An electron-pair distribution function has been derived. The function was used to obtain a distribution curve for crystalline BaO"2B2 03. The similarity of this curve and the curve for

vitreous barium borate (1:1.7) indicates similar short-range order in

the crystal and the glass. A paper concerning the distributions of

alkaline-earth cations in vitreous borates (Block and Piermarini,,

1964a) presents a detailed discussion of these results.

5.8 Allotropy in the Rare Earth Metals

G. J. Piermarini and C. E. Weir,

Crystallography Section

The survey of effects of pressure on the structures of the rare earth metals (NBS Technical Note 236, Section 5.6) is being continued.

A paper on the allotropic modifications in lanthanum, cerium, praseodynium, and neodynium has been published (Piermarini and Weir, 1964)

and work on the structures of the metals samarium, gadolinium, and

terbium up to pressures of 35 - 40 kb has been completed using the

high-pressure x-ray powder diffraction camera described earlier

[Piermarini and Weir, J. Research NBS 66A, 325 (1962)]. These studies

revealed no new allotropic forms in this pressure range. Cerium

metal was studied at pressures up to about 120 kb. The electronic

transition (fee to "collapsed" fee) occurring at about 7.5 kb was corroborated, and, in addition, evidence for a second allotropic form

which has been reported was found at pressures of 110 - 120 kb. Further

investigation of this new form is planned.

The high pressure x-ray camera has been substantially redesigned

to provide a greater angular range. This camera will be used in subsequent studies on the rare-earths.

57
5.9 Infrared Studies of Inorganic Materials

C. Weir and R. A. Schroeder,

Crystallography Section

Infrared studies of B^° and B^^ substituted anhydrous borates were carried out in the 2000 cm"^ - 300 cm~^ range. Spectral bands for all

ortho-, pyro-, and some meta-borates could be assigned satisfactorily.

From correlations between spectra and structure, it appears that boron

in 3 fold or in 4 fold coordination can be identified on the basis of

the infrared spectrum alone. Triangularly coordinated boron is characterized by the presence of strong, broad absorption in the 1100 cm~-'--1300

cm~^ region. In addition, there is absorption in the 700 cm~^ region.

Both of these characteristic bands are strongly dependent on isotope

mass and thus isotopic substitution can be used to differentiate these

bands from others occurring in these regions.

The most characteristic feature of tetrahedrally coordinated boron

is the presence of strong, broad absorption in the 800 cm~^ -1100 cm~^

region. , Also, absorption bands which are not sensitive to isotope mass and therefore can be distinguished from triangular boron, occur in the

700-800 cm~^ region (Weir and Schroeder, 1964). These studies were

used to predict that tetradedral coordination of boron occurs in

SrB^O^ . This was confirmed by single crystal studies.

5.10 Structure Models for Amorphous and Crystalline

Phases of Simple Substances

Fred Ordway,

Inorganic Materials Division

Computer routines have been completed for processing measurements

on the random tetrahedral network of 300 units. Computations include:

coordinates from angle measurements; generations of remaining points

of a unit when only three are known; generation and deletion of coordinate listings implied by topological data; checking dimensions of units;

reconciling multiple sets of coordinates for the same point; checking

sets for completeness; tabulating distributions of distances and angle,

listing those beyond tolerance limits; and adjusting positions for best

agreement with ideal distances. Coordinate data for the model have

been completed and adjusted, and some of the distributions calculated.

Aspects of the work were described in lectures at Corning Research

Laboratories, Alfred University, and Harvard University, and in a publication (Ordway 1964)

.

58
5.11 Crystal Chemistry of Silver Iodide*

G. Bur ley,

Crystallography Section

Previous work in this area was discussed in NBS Technical Note 236.

Studies of the kinetics and mechanism of the low-cubic to hexagonal

phase transformation (Hurley, 1964a) and of an x-ray determination of

the Debye temperature of silver iodide (Bur ley, 1964b) have been published. A paper discussing an x-ray investigation of strain in silver

iodide as well as another treating the ice nucleation by photolyzed

silver iodide particles have been accepted for publication. An

analysis of the radial distribution data of powder x-ray diffraction

data from both the low-cubic and hexagonal phases just above the transition temperature of both to the high-cubic structure at 147 °C is con- tinuing.

5.12 A New High-Resolution Small-Angle X-Ray Camera

H. Brumberger** and R. Deslattes

Crystal Chemistry Section

This instrument was described in NBS Technical Note 236, Section

5.12,. The following is the abstract of a paper (Brumberger and Deslattes,

1964^:

"A novel small-angle x-ray camera, utilizing

the Borrmann effect in the 220 Laue reflection

from germanium to form the incident beam, has

been designed and tested. A test pattern of

amorphous carbon showed angular resolution

to nearly 2000 1. In principle, an improvement of resolution by an order of magnitude

is possible."

5.13 Spectroscopy of Diatomic Impurities in

Rare-Gas Crystalline Matrices

L. Pollack,

Crystal Chemistry Section

The abstract of a paper published during the reporting period

follows (Pollack and Pollack, 1964)

:

"Examination of absorption spectra of molecules

in liquid and crystalline matrices gives

*Research supported by the Atmospheric Sciences Program, National

Science Foundation, NSF Grant G 19648

**0n research leave of absence from Dept. of Chemistry, Syracuse University, Syracuse 10, N. Y.

59
information on two fundamental kinds of

problems: perturbations of molecules by

surrounding fields, and effects of impurities on crystals and crystal growth. Raregas solid and liquid matrices are ideally

suited to such problems since the forces between rare-gas atoms are especially weak,

symmetric, short-range, and well known. Experimental studies of growth and observation

of pure rare-gas crystals, transparent in a broad :^ange from the infrared to the vacuum

ultra-violet, and of low concentrations of

diatomic molecules in solid solution with

rare gases are described. As an example, the

system NO in liquid and crystalline Kr was studied in the range from 2000-5000 A. Even

at the smallest concentrations of NO no trace

of discrete spectra of the NOy system was

found. However, a cutoff at short wavelength

was observed in the liquid, increasing with

NO concentration. This absorption cutoff may

be due to the transition from the ground state

X^n to the theoretically predicted *n state.

Both spectroscopic and solid state conclusions

are drawn from these experiments and experiments

on other systems of the same kind."

5.14 Crystal - Field Studies by Matrix Spectroscopy

D. E. Mann,

Molecular Spectroscopy Section

The extensive investigation by infrared "spectra of HCl and~DCl

in solid argon and krypton has been completed. In addition to demonstrating the existence of molecular rotation the results provided new evidence of the influence of impurities on the spectra and motions of

the diatomic species and showed the theoretical analysis formulated

by Flygare to be incorrect. The study of other diatomic molecules, including HBr and CO, in rare-gas matrices is being continued along

the lines already developed for HCl with promising results.

60
5.15 Phase Equilibria Determination with the Aid of

Crystal Structure Analysis

R. S. Roth*,

Crystallography Section

and

A. D, Wads ley**

The crystal structures of the compounds PgNb^^gOgo and

TiNbg^Ogg vfevB determined by x-ray methods. Knowledge of the structure

of these compounds of NbgOg , and of other titano-niobates was used to

predict phases that might be expected to occur in other chemical

systems involving NbgOg.

In the system NbgOg-WOg, five new compounds, three monoclinic and

two tetragonal, were found in the composition range - 5170WO3 which

had previously been described as a solid solution range. The crystal

structures of four of these compounds were determined and some general

rules for the occurrence of various phases in niobate systems were

formulated. The phase equilibrim diagram for the entire system

NbgOg- WO,, is now being determined, and the crystal structure of other

compounds in the system is under investigation.

A paper on composition of the phases in the systems NbOg-NbgOg

and TiOg-NbgOg (Roth, Wadsley, and Gatehouse, 1964) has been published.

A second on mixed oxides of titanium and niobium and the crystal

structure of TiOg'12NbgOg (Roth and Wadsley, 1964) has been accepted,

and a third on the crystal structure of PgOg'9NbaOg is in preparation.

5.16 Ultrasonic Measurements at Pressure-Induced

Polymorphic Phase Changes

P , Heydemann

,

Pressut'e Measurements Section

An attempt will be made to measure the change of the elastic

constants and of the internal friction of crystals at ultrasonic frequencies during pressure-induced changes of their crystal structure.

These measurements will be combined with electrical and PVT-measurements . Among the materials to be studied are potassium chloride and

bismuth. Both single and polycrystalline samples will be used. An

apparatus is being developed which will allow the determination of the

transition pressures with great precision.

* This work was completed at CSIRO, Melbourne, Australia while

Dr. Roth was on Educational Leave. He has since returned to NBS

.

** Dr. A. D. Wadsley, Mineral Chemistry Division, CSIRO, Melbourne,

Australia.

61
5.17 Microcompositlon and Structure Characterization

by Electronprobe Methods

H. Yakowitz and D. Vieth

Lattice Defects and Micros true tures Section

and

J. R. Cuthill

Alloy Physics Section

An electronprobe microanalyzer was built at NBS before commercial

instruments became available. Chemical analyses of regions of the order

of one micron in diameter can be made in situ by excitation of such a region with a focused beam of electrons and analysis of the characteristic x-ray emission produced. One of the studies made with this instrument was a study of the uniformity of chemical composition of the NBS

461 standard steel sample (Michaelis , Yakowitz, and Moore, 1964). This

standard sample material was found to be chemically uniform at the

two to four micron level of spatial resolution.

This original NBS electronprobe has been rebuilt with a higher

take-off angle to permit analysis of the light elements, and with provision for obtaining Kossel patterns. The Kossel pattern technique is

the most sensitive and accurate method for obtaining local changes in

lattice spacings, as might be introduced by local strains, and the

electronprobe is ideally suited to this technique. The first-named

of the above investigators has just returned after a year of study at

MIT under Prof. Ogilvie, acquiring experience in applying the Kossel

technique with the electronprobe.

6. PARTIAL LIST OF PARTICIPANTS

There follows a partial list of scientists engaged in activities

described in this note, with indications of their research fields and

organizational location within the National Bureau of Standards. The

latter may be helpful in making contact with individuals for the purpose of obtaining reprints or further technical information.

Participants at the Washington Laboratories ; Abramowltz . S tan ley : Ph.D. Polytechnic Inst, of Brooklyn, 1963; infrared molecular spectra; Heat Division Author: 5.3

Allen . Harry C . . Jr . ; Ph.D. University of Washington 1951; electronspin-resonance studies; Chief, Inorganic Materials Division

Author: 4.8

Ambler, Ernest : Ph.D. Oxford University, 1953; nuclear reactions,

low- temperature magnetism; Chief, Cryogenic Physics Section, Heat

Division Author: 4.21

Barber , David J . : Ph.D. University of Bristol, 1959; growth perfection

of crystals; Physical Properties Section, Inorganic Materials Division * Author; 3.11

Bass. Arnold M .: Ph.D. Duke University 1949; molecular spectroscopy;

Heat Division

62
Becker, James H . ; Ph.D. Cornell University, 1957; optical and transport properties of semiconductors; Solid State Physics Section, Atomic

Physics Division Author: 4.21, 4.4

Bennett, Laurence H .: Ph.D. Rutgers University, 1958; nuclear resonance

studies; Chief, Alloy Physics Section, Metallurgy Division Author: 3.8

Block, Stanley : Ph.D. Johns Hopkins University, 1955; x-ray crystallography; Crystallography Section, Inorganic Materials Division

Author: '5.4, 5.7

Blunt , Robert F . : Ph.D. Rice University, 1949; optical properties

of solids; Solid State Physics Section, Atomic Physics Division

Author: 3.1

Bolz, Leonard H .: Crystal perfection by electron microscopy; Physical

Properties Section, Inorganic Materials Division

Bowman, Horace A .: Cartesian diver; Mass and Volume Section, Metrology

Division Author: 4.19

Breen , David E . ; Inter- and intramolecular properties of organic molecules, crystals, and rigid glasses; Physical Chemistry Division

Author: 4.16

Brower . William S . : Crystal growth by Verneuil process and floatingzone technique; Crystal Chemistry Section, Inorganic Materials Division Author: 2.6

Brown, Walter E .: Ph.D. Harvard University, 1949; solubility and

crystallography of calcium phosphate; Dental Research Section, Pol3nners

Division Author: 5.5

Bur ley, Gordon : Ph.D. Georgetown University, 1962; crystallography of

silver iodide; Crystallography Section; Inorganic Materials Division

Author: 4.17, 5.11

Calvert, Joan P .: Growth of oxide films; Corrosion Section, Metallurgy Division

Capps , Webster : Physics and chemistry of glass; Glass Section, Inorganic Materials Division

Cataland, George : Low-temperature thermometry; Cryogenic Physics Section, Heat Division

Chang, Te-Tse : Ph.D. Univ. of Colorado, 1962; magnetic resonance; Solid

State Physics Section, Atomic Physics Division Author: 3.15

Cohen, Martin L : X-ray diffraction studies of crystals grown at high

temperatures; Solid State Physics Section, Atomic Physics Division

Author: 3.2

Cook, Richard K. : Ph.D. University of Illinois, 1935; acoustics and

solid state physics; Chief, Sound Section, Mechanics Division

Comeford, J.J .: Molecular spectroscopy; Molecular Spectroscopy Section,

Physical Chemistry Division Author: 5.3

Cooter , Irvin L . : Nuclear magnetic resonance in garnets; Chief, Magnetic Measurements Section, Electricity Division

Coriell, Sam R .: Ph.D. Ohio State University, 1961; mathematical

physics; Crystallization of Metals Section, Metallurgy Division

Author: 2.3

Cuthill, J.R .: Ph.D. Purdue University, 1952; soft x-ray spectroscopy,

electroprobe electron analysis; Alloy Physics Section, Metallurgy

Division Author: 5.17

deKoranyi, Alexandra : Crystal growth by electrodeposition; Electrolysis

and Metal Deposition Section, Metallurgy Division Author: 3.6

Deslattes, Richard D .: Ph.D. Johns Hopkins University, 1959; x-ray

spectroscopy; Crystal Chemistry Section, Inorganic Materials Division

Author: 3.14, 4.5, 4.15, 5.12

deWit, Roland : Ph.D. University of Illinois, 1959; dislocation theory;

Lattice Defects and Microstructures Section, Metallurgy Division

Author: 3.5

Dickson, Robert W .: Homogeneous stress on oxide structures, dislocation studies by x-ray methods: Physical Properties Section, Inorganic Materials Division Author: 2.1

Dove, Robert B . : Nuclear magnetism; Cryogenic Physics Section, Heat

Division

63
Dueker. Heyman C : Ph.D. University of Maryland, 1964; physical chemistry of glasses; Glass Section, Inorganic Materials Division Early. James G.: Ph.D. Rennsalaer Polytechnic Inst., 1963; kinetics

of crystallization; Crystallization of Metals Section, Metallurgy Division Author: 2.2

Eby. Ronald K .

: Ph.D. Brown University, 1958; acoustics, polymer

physics; Polymer Physics Section, Polymers Division Author: 2.19 Edlow. Martin E . : Low- temperature thermometry; Cryogenic Physics Section, Heat Division

Eisenstein. Julian C : Ph.D. Harvard University, 1948; low temperature

magnetism; Cryogenic Physics Section, Heat Division

Escalante, Edward : Field emission; Corrosion Section, Metallurgy

Division

Evans, Eloise H .: Physical chemistry, x-ray diffraction; Crystallography

Section, Inorganic Materials Division, A.S.T.M. Fellowship supported Farabaugh, Edward N .: Etch-pits crystal orientation; Crystal Chemistry

Section, Inorganic Materials Division Author: 4.1

Fo ley, Carol L . ; Growth of oxide films; Corrosion Section, Metallurgy

Division Author: 3.7

Forman, Richard A .: Nuclear and quadrupole resonances; Solid State

Physics Section, Atomic Physics Division Author: 3.15

Franklin, Alan D .: Ph.D. Princeton University, 1949; properties of point

defects in crystals; Inorganic Materials Division

Frederickse, Hans P. R .: Ph.D. Leiden University, 1950; semiconductors

at low temperatures; Chief, Solid State Physics Section, Atomic

Physics Division Author: 4.4

French, Judson C . : Solid state devices and materials; Electron Devices

Section, Instrumentation Division Author: 3.10

Frolen , Lois J .: Ph.D. Pennsylvania State University, 1963; spectroscopy,

crystallography, microscopy; Polymers Division Author: 2.14, 2.15

Glasgow, Augustus R .: D.Sc. University of Brussels, 1957; preparation

and purification of pol5niieric forms, phase equilibria, purity determinations at high pressures; Analytical and Purification Section, Analytical Chemistry Division Author: 2.8, 5.2

Gornick, Fred : Ph.D. University of Pennsylvania, 1959; physical

chemistry of high polymers; Pol5raiers Division Author: 2.15

Grabner , Ludwig H . : Ph.D. Columbia University, 1950; semiconductors,

photoconductivity; Solid State Physics Section, Atomic Physics Division Author: 4.22

Hall, L. H .: Ph.D. Johns Hopkins University, 1963; crystal structures;

Crystallography Sectiort, Inorganic Materials Division Author: 5.4

Haller, Wolfgang K . : Ph.D. University of Vienna, 1950; physical

chemistry of glasses; Glass Section, Inorganic Materials Division

Hardy, Stephen C : Vapor growth of metal crystals; Crystallization

of Metals Section, Metallurgy Division Author: 2.4

Harman , George G .: Solid state physics, surface phenomena and electroluminescence; Electron Devices Section, Instrumentation Division

Author: 3.10

Heydemann , Peter : Ph.D. University of GOttingen, 1958; physical acoustics, mechanical and electrical properties of polymers; Pressure

Measurement Section Author: 5.16

Hoffman, John D .: Ph.D. Princeton University, 1949; dielectrics,

nucleation rate of polymer crystals; Chief, Polymers Division

Holly, Sylvanus : Crystal growth; Crystal Chiemistry Section, Inorganic

Materials Division

Horton, Avery T .: Crystal growth, impurity retention; Crystal Chemistry

Section, Inorganic Materials Division Author: 2.7

Hosier, William R .: Electronic transport phenomena; Solid State

Physics Section Author: 4.4, 4.21

Howard, Robert E .; Ph.D. Oxford University, 1957; theoretical physics;

Chief, Metal Physics Section, Metallurgy Division Author: 2.20, 3.5

64
Hudson , Ralph P . ; Ph.D. Oxford University, 1949; low- temperature magnetism; Chief, Heat Division Author: 4.9

Hyman , A . ; Ph.D. Rutgers,. 1964; physical chemistry; Crystallography

Section, Inorganic Materials Division Author: 5.7

Ives, Lewis K .: Electron microscopy; Lattice Defects and Microstructures Section, Metallurgy Division Author: 3.3

Jackson, Ronald W .: Ph.D. University of Bristol, 1950; thermodynamics

of sucrose solutions, kinetics of growth of sucrose crystals; Crystal

Chemistry Section, Inorganic Materials Division Author: 2.12

Kaeser, Robert S .: Low-tempei^iature magnetism, cryogenics; Cryogenic

Physics Section, Heat Division

Kahn, Arnold H . : Ph.D. University of California, 1955; electronic

energy levels of solids; Solid State Physics Section, Atomic Physics

Division Author: 4.3

Keezer . Richard C . : Optical properties and physical chemistry of

semiconductors; Solid State Physics Section, Atomic Physics Division

Author: 4.4, 4.22

Keller. Richard A .; Ph.D. University of California, 1961; inter- and

intramolecular properties of organic molecules, crystals, and rigid

glasses; Physical Chemistry Division Author: 4.16

Khoury, Fred : Ph.D. Leeds University, 1956; morphology and crystallization of poljnners; Polymer Physics Section, Polymers Division

Author: 2.17

Klein. Ralph : Ph.D. University of Pittsburgh, 1950; fie Id- emission

and low- temperature chemistry; Chief, Surface Chemistry Section,

Physical Chemistry Division

Kokoszka , Gerald F . : Electron-spin-resonance studies; Inorganic Materials Division Author: 4.8

Kruger, Jerome : Ph.D. University of Virginia, 1953; corrosion reactions at metal surfaces; Corrosion Section, Metallurgy Division

Author: 3.7

LaVilla, Robert E .: Ph.D. Cornell University, 1960; diffraction

techniques; Crystal Chemistry Section, Inorganic Materials Division

Author: 4.5

Levin. Ernest M .; Phase equilibria of oxide systems; Crystallography

Section, Inorganic Materials Division Author: 5.6

Lippincott, Ellis R .: Ph.D. Johns Hopkins University, 1947; infrared spectroscopy; Crystallography Section, Inorganic Materials Division

Macedo , P . B . : Ph.D. Catholic University, 1963; viscoelastic properties; Glass Section, Inorganic Materials Division

Mangum, Billy W .: Ph.D. University of Chicago, 1961; low- temperature

magnetism; Cryogenic Physics Section, Heat Division. Author: 4.9

Mann , David E . : Ph.D. University of Chicago, 1948; spectroscopy;

Chief, Molecular Spectroscopy Section, Physical Chemistry

Author: 5.14

Mante. Alexander J. H .: NATO Fellow (1963-1964); theomoelectricity;

Solid State Physics Section, Atomic Physics Division. Author: 4.4

Margoshes . Marvin : Ph.D. Iowa State University, 1953; spectrographic

analysis; Spectrochemical Analysis Section, Analytical Chemistry

Division Author: 3.9

Marshak, Harvey : Ph.D. Duke University, 1955; nuclear reactions,

cryogenics; Cryogenic Physics Section, Heat Division

Martin, G.M .; Polymer physics; Polymer Physics Section, Pol3miers Division Author: 2.18

Marvin , Robert S . : Ph.D. University of Wisconsin, 1949; rheology and

polymer physics; Chief, Rheology Section, Mechanics Division

Marzullo, Sam: Dielectric properties; Physical Properties Section,

Inorganic Materials Division

Mauer, Floyd A .: Instrumentation for crystallography; Crystallography

Section, Inorganic Materials Division Author: 3.16

McMurdie , Howard F . : Crystallography and chemical phase studies; Chief,

Crystallography Section, Inorganic Materials Division

65
McNish, Alvin G .: Precise density determinations for solid materials;

Chief, Metrology Division

Mebs , Russell W . : Ph.D. Ohio State University, 1940; nuclear acoustic

resonance; Alloy Physics Section, Metallurgy Division

Melmed, Allen J . : Ph.D. Pennsylvania State University, 1958; surface

studies by field emission; Corrosion Section, Metallurgy Division

Author: 2.5

Miller, Paul R . ; High- temperature crystal growth, crystal orientation;

Crystal Chemistry Section, Inorganic Materials Division. Author: 4.1

Milligan . Dolphus E . ; Ph.D. University of California, 1958; molecular

spectroscopy; Molecular Spectroscopy Section, Physical Chemistry

Division

Moreno , E . D . : Ph.D. University of Calfornia, 1957; physical chemistry

of calcium phosphates; Dental Research Section, Polymers Division

Author: 5.5

Morris , Marlene C . : Physical Chemistry, x-ray diffraction; Crystallography Section, Inorganic Materials Division; A.S.T.M. Fellowship supported

Newton, Clarence J .: Ph.D. University of Texas, 1952; x-ray crystallography of metals; Lattice Defects and Micros true tures Section, Metallurgy Division Author: 3.4

Ogburn. Fielding: Electrochemistry, electrodeposition; Electrolysis

and Metal Deposition Section, Metallurgy Division Author: 2.10, 3.6

Ondik.' Helen M . ; Ph.D. Johns Hopkins University, 1957; crystallography,

inorganic chemistry; Crystallography Section, Inorganic Materials

Division Author: 5.4

Ordway, Fred : Ph.D. California Institute of Technology, 1949; x-ray

crystallography; Inorganic Materials Division Author: 5.10

' Orem, Theodore H .: Mechanisms of corrosion processes; Crystallization

of Metals Section, Metallurgy Division Author: 2.1

Oser , Hans J . : Ph.D. University of Freiburg, 1957; boundary value problems; Applied Mathematics Division Author: 2.20

Paretzkin, Boris : Study of perfection of single crystals by x-ray

diffraction; Crystal Chemistry Section, Inorganic Materials Divisiort

Author: 2.11, 3.15

Parker , Harry S . ; Ceramic engineering; Crystal Chemistry Section, Inorganic Materials Division Author: 2.12

Parker , Robert L . : Ph.D. University of Maryland, 1960; growth of

crystals; Chief, Crystallization of Metals Section, Metallurgy Division

Author: 2.1, 2.2, 2.3, 2.4, 2.20

Passaglia, Elio : Ph.D. University of Pennsylvania, 1955; mechanical

relaxation processes in poljrmers; Polymer Physics Section, Polymers

Division Author: 2.18

Payne , Richard E . : Nuclear resonance; Solid State Physics Section;

Atomic Physics Divis ion

Peiser, H. Steffen: Crystallography and crystal chemistry; Chief,

Crystal Chemistry Section, Inorganic Materials Division.

Author: 2.10, 4.2

Perloff , Alvin : Structure analysis; Crystallography Section, Inorganic

Materials Division Author: 5.4

Pfeiffer. Earl R .; Crystal growth from solution; Cryogenic Physics

Section, Heat Division

Piermarini, Gasper J .: Radial-distribution studies, high-pressure

x-ray diffraction studies; Crystallography Section, Inorganic Materials

Division Author: 5.7, 5.8

P lumb , Harmon H . : Ph.D. Northwestern University, 1954; low- temperature

thermomen try ; Cryogenic Physics Section, Heat Division

Poland, Duncan E .: Ph.D. University of Wisconsin, 1963; physical chemistry and" transport properties of solids; Solid State Physics Section,

Atomic Physics Division Author: 4.4

Pollack. Gerald L .: Ph.D. California Institute of Technology, 1962;

low- temperature physics; Crystal Chemistry Section, Inorganic

Materials Division Author: 5.13

66
Pontius, Paul E .: Accurate measurements of mass volume and density;

Chief, Mass and Volume Section, Metrology Division

Proctor, Thomas M .: Solid state physics; Sound Section, Mechanics

Division Author: 4.18

Rasberry, Stanley D .r Spectrographic analysis; Spectrochemical

Analysis Section, Analytical Chemistry Division Author: 3.9

Read, Susan F . J

.

: Ph.D. Oxford University, 1963; solid state physics;

Temperature Physics Section, Heat Division

Robbins . Carl R .: Phase-rule equilibria of inorganic systems; Crystallography Section, Inorganic Materials Division

Roberts, D. Ellis : Crystal growth; Solid State Physics Section, Atomic

Physics Division Author: 2.9

Robinson, Henry E .: Thermal conductivity, measurements on solids at

high and low temperatures; Chief, Heat Transfer Section, Building Research Division

Ross , GayIon S . ; Nucleation, crystal growth; Polymers Division

Author: 2.14, 2.15

Roth, Robert S . : Ph.D. University of Illinois, 1951; x-ray diffraction

studies, phase equilibria; Crystallography Section, Inorganic Materials

Division Author: 5.6, 5.15

Rubin, Robert J .: Ph.D. Cornell University, 1951; theoretical chemical

physics; Heat Division

Rubin, Sherwin : Electronic engineering; Engineering Electronics Section, Instrumentation Division Author: 4.6

Ruff. Arthur W. , Jr .; Ph.D. University of Maryland, 1963; dislocations

and etch pits; Chief, Lattice Defects and Microstructures Section,

Metallurgy Division Author: 3.3, 3.4

Ruthberg, Stanley ; Materials and physics of vacuum devices; Electron

Devices Section, Instrumentation Division

Saylor, Charles P .: Ph.D. Cornell University, 1928; precise characteristics of compounds, accurate microscopic measurements of optical properties; Analytical Chemistry Division

S chaff t, Harry A. : Semiconductor devices and breakdown phenomena;

Electron Devices Section, Instrumentation Division Author: 3.10

Schneider, Samuel J .: Phase equilibria of oxide systems and meltingpoint standards; Crystallography Section, Inorganic Materials Division

Author: 4.14

Schooley, James F .: Ph.D. University of California, 1961; crystal

growth for low- temperature paramagnetic studies; Cryogenic Physics

Section, Heat Division Author; 4.21

Schoonover, Irl C : Ph.D. Princeton University, 1933; research administration; N. B. S. Deputy Director

Schoonover, R. M .: Density determination; Mass and Volume Section,

Metrology Division Author: 4.19

Scribner, Boudon F . : Analytical applications of optical and x-ray

spectroscopy; Chief, Spectrochemical Analysis Section, Analytical

Chemistry Division Author: 3.9

S immons , John A . : Ph.D. University of California, 1961; mathematical

physics; Metal Physics Section, Metallurgy Division Author: 2.20

Spinner, Sam: Elastic properties of inorganic solids; Physical Properties Section, Inorganic Materials Division Author: 3.13, 4.11

Sober , A. J . : Inorganic chemistry; Crystal Chemistry Section, Inorganic Materials Division Author: 2.13

Streever, Ralph L .: Ph.D. Rutgers University, 1960; nuclear magnetic resonance; Magnetic Measurements Section, Electricity Division

Author: 4.13

Swans on, Howard E .: Physical chemistry, x-ray diffraction; Crystallography Section, Inorganic Materials Division Author: 5.1

Swartzendruber , Lydon J .: Solid state physics; Electron Devices Section, Instrumentation Division Author: 3.10

Termini, Dominic J .: Nucleation and crystal growth; Analytical

Chemistry Division

67
Thurber, Willis R .: Thermoelectricity; Solid State Physics Section,

Atomic Physics Division Author: 4.4

Tighe, Nancy J . : Defect studies by electron microscopy of non-metallic

crystals; Physical Properties Section, Inorganic Materials Division

Author: 3.11

Torgesen, John L .: Ph.D. Columbia University, 1942; crystal growth

from solutions, impurity retentions, crystal properties; Crystal

Chemistry Section, Inorganic Materials Division. Author: 2.7, 2.12, 2.13

Trisch, Ronald C : Nuclear magnetic resonance; Solid State Physics

Section, Atomic Physics Division

Vieth, P .: Electronprobe microanalysis; Lattice Defects and Microstructures Section, Metallurgy Division Author: 5.17

Wachtman , John B., Jr .: Ph.D. University of Maryland, 1961; mechanical

and electrical properties of crystals; Chief, Physical Properties

Section, Inorganic Materials Division Author: 3.13, 4.11, 4.2

Wagman, Donald D .; Thermochemistry and chemical thermodynamics;

Chief, Thermochemistry Section, Physical Chemistry Division

Wasilik, John H. : Ph.D. Catholic University, 1956; dielectric constant

and losses, ultrasonics; Solid State Physics Section, Atomic Physics

Division Author: 4.7

Weeks , James J . : Measurements of dielectric properties of polymers,

crystallization and melting of polymers; Dielectric Section, Electricity

Division Author: 2.16

Weir, Charles E .: Infrared spectroscopy and high-pressure physics;

Crystallography Section, Inorganic Materials Division. Author: 5.8, 5.9

Wiederhorn , Sheldon M .: Ph.D. University of Illinois, 1960; optical

properties of high pressure, fracture of solids; Physical Properties

Section, Inorganic Materials Division Author: 4.12

Will , Richard S . : Electron-field emission; Electron Physics Division

Williams, Robert S.: Solid state; Crystal Chemistry Section, Inorganic

Materials Division

Winogradoff, N .: Ph.D. University of Edinburgh, 1945; interaction of

radiation with matter; Electron Devices Section, Instrumentation

Division Author: 3.10

Yakowitz , H . : X-ray microdiffractlon, electronprobe microanalysis;

Lattice Defects and Microstructures Section, Metallurgy Division

Author: 5.17

Yolken, Howard T .: Growth of oxide films; Corrosion Section, Metallurgy Division

Young, John D . : Crystal growth by electrodeposition; Electrolysis and

Metal Deposition Section, Metallurgy Division

Participants at the Boulder Laboratories

Arp , Vincent D . : Ph.D. University of California, 1959; superconductivity;

Cryogenic Properties of Solids Section, Cryogenic Engineering Laboratories Author: 4.20

Bamberger , Edwin C . : Dielectric measurements; Radio and Microwave

Materials Section, Radio Standards Physics Division

Bussey, Howard E .: Ph.D. University of Colorado, 1964; magnetism and

ferrites ; Radio and Microwave Materials Section, Radio Standards Physics

Division Author: 4.10

Cook, Alan R . : Physical instrumentation; Radio and Microwave Materials

Section, Radio Standards Physics Division Author: 3.12

Dalke, John L . : Characterization of materials at radio frequencies;

Chief, Radio and Microwave Materials Section, Radio Standards Physics

Division

Gruzensky, Paul M. : Ph.D. Oregon State College, 1959; physical chemistry and high-purity materials; Radio and Microwave Materials Section,

Radio Standards Physics Division

68
Guntner, Charles S .: Imperfections, flow and fracture, phase transformations; Properties of Materials Section, Cryogenics Engineering

Laboratories

Jefferson, Clinton F .: Ph.D. University of Michigan, 1959; solid

solution for ferrimagnetic characterists ; Radio and Microwave Materials

Section, Radio Standards Physics Division

Mahler, Robert J .: Ph.D. University of Colorado, 1963; solid state

physics; Radio and Microwave Materials Section, Radio Standards Physics

Division Author: 3.12

Matarrese, Lawrence M .: Ph.D. University of Chicago, 1954; solid

state physics, EPR resonance spectroscopy related to solid state mechansims; Radio and Microwave Materials Section, Radio Standards Physics

Division Author: 3.12

Peterson, Robert L. : Ph.D. Lehigh University, 1959; theoretical

physics; Radio and Microwave Materials Section, Radio Standards Physics

Division Author: 3.12

Powell, Robert L .: Thermal and electrical conduction of metals at

low temperatures; Properties of Materials Section, Cryogenic Engineering Laboratory

Reed, Richard P .: Imperfections, flow and fracture, phase transformations; Properties of Materials Section, Cryogenic Engineering Laboratory

Risley , Alan S . : Magnetism and ferrites; Radio and Microwave Materials

Section, Radio Standards Physics Division Author: 4.10

Wells . Joseph S . : Ph.D. University of Colorado, 1964; microwave physics,

solid state physics relating to ENDOR and ^MR; Radio and Microwave

Materials Section, Radio Standards Physics Division Author: 3.12

Winder, Dale R . : Ph.D. Case Institute of Technology, 1957; solid

state physics; Radio and Microwave Materials Section, Radio Standards

Physics Division

7. LITERATURE REFERENCES

H. C. Allen, G. F. Kokoszka, and R. G. Inskeep, (1964); The EPR

Spectrum of Some Tris Complexes of Cu*^; J. Am. Chem. Soc, 86, 1023.

S. Block and G. Piermarini, (1964a); Alkaline-earth cation Distributions in Vitreous Borates; Phys . & Chem. of Glass, (accepted).

H. Brumberger and R. Deslattes, (1964); A New High-Resolution SmallAngle X-Ray Camera; J. Res. Natl. Bur. Std., 68C, (3), 173-5.

G. Bur ley, (1964a); Kinetics and Mechanism of the Low-Cubic to Hexagonal Phase Transformation of Silver Iodide; J. Phys. Chem. ^, 1111.

G. Bur ley, (1964b); An X-Ray Determination of the Debye Temperature of

Silver Iodide; J. Phys. Chem. Solids, 25, 629.

S. R. Coriell and R. L. Parker, (1964); Stability of a Cylinder Growing in a Diffusion Field; J. Appl. Phys., (accepted).

A. B. Denison, L. W. James, J. D, Curran, W. H. Tanttlia, and R. J.

Mahler, (1964); Ultrasonic Induced Nuclear Spin Transison in Antiferromagnetic KMnFg; Phys. Rev. Letters, _12, 244.

R. D. Deslattes, J. T. Torgesen, B. Paretzkin, and A. T. Horton, (1964);

Preliminary Studies on the Characterization of Solution-Grown ADP

Crystals; Thirteenth Annual Conference on Applications of X-Ray Analysis; Denver, Colorado, August, 1964. Proceedings of that conference.

Vol. 8, to be published by Plenum Press, New York. Will be available

about June, 1965.

69
R. deWit and R. E, Howard, (1964); Thermodynamics of Segregation of

Solute Atoms; Bull. Am. Phys . Soc, 9, 242.

R. K. Eby, (1964); A Copolymer with Lamellar Morphology; J. Res. Natl.

Bur. Std. , 68A, 269.

H. P. R. Frederikse, W. R. Thurber, and W. R. Hosier, (1964); Electronic

Transport in Strontium Titanate; Phys. Rev., 134 , A44a

.

A. H. Kahn, H. P. R. Frederikse, and J. H. Becker, (1963); Electron

Energy Bands in SrTiOg and TiOg (Theory and Experiment) ; Proceedings

of the Buhl Conference on Transition Metal Compounds (held in October,

1963).

A. H. Kahn and A. J. Leyendecker, (1964); Electronic Energy Bands in

SrTiOg and Related Oxide Semiconductors; Proceedings of the 1964

International Conference on the Physics of Semiconductors, Paris, July,

1964.

A. H. Kahn and A. J, Leyendecker, (1964); Electronic Energy Bands in

Strontium Titanate; Phys. Rev., (to appear August 31, 1964).

J. Kruger and C. L. Foley, (1964); J. Electrochem, Soc. Ill , No. 8,

Abstracts of Fall Meeting.

E. M. Levin and R. S. Roth, (1964); Polymorphism of Bismuth Sesquioxide.

I. Pure BigOg . II. Effect of Oxide Additions on the Polymorphism

of BigOg; J. Res. Natl. Bur. Std., ^8A, (2), 189 and 197.

P. B. Macedo, W. Capps , and J. B. Wachtman, Jr., (1964); Elastic Constants of Single Crystal ThO^ at 25 °C prepared for J. Am. Ceram. Soc.

R. E. Michaelis, H. Yakowitz, and G. A. Moore, (1964); Metailographic

Characterization of an NBS Spectrometric Low-Alloy Steel Standard;

J. Res. Natl. Bur. Std., 6^, 343-354.

F. Ogburn, (1964); Growth Twins and Branching of Electrodeposited

Copper Dendrites; J. Electrochem. Soc, 111 , 870.

F. Ogburn, B. Paretzkin, and H. S. Peiser, (1964); Pseudopentagonal

Twins in Electrodeposited Copper Dendrites; Acta Cryst., _17, 774.

H. M, Ondik, (1964a); The Structure of the Triclinic Form of Sodium

Tetrametaphosphate Tetrahydrate; Acta Cryst., (accepted).

H. M. Ondik, (1964b); The Structures of Anhydrous Sodium Trimetaphosphate,

NagPgOg, and the Monohydrate , NagPgOe'HgO; Acta Cryst., (accepted).

F. Ordway, (1964); Condensation Model Producing Crystalline on Amorphous , Tetrahedral Network; Science, 143, 800-801. f G. J. Piermarini and S. Block, (1963); Radial Distribution Study of j Vitreous Barium Borosilicate; J. Res. Natl. Bur. Std., 67A , 37.

| G. J. Piermarini and C. E. Weir, (1964); Allotropy in Some Rare-Earth

Metals at High Pressures; Science 144 , 69.

70
G. L. Pollack and A. A. Pollack, (1964); Absorption Spectra of

Diatomic Molecules in Liquid and Crystalline Rare Gases; Developments

in Applied Spectroscopy, Vol. 3 ; 376-82 Plenum Press, New York.

J. M. Reber, (1964); Potential Distribution in a Rectangular Semiconductor Bar for use with Four-Point Probe Measurements; Solid-State

Electronics (accepted)

.

A. S. Risley and H. E. Bussey, (1964); Ferromagnetic Resonance Relaxation, Wide Spin-Wave Coverage by Ellipsoids; J. Appl. Phys . _35^, 896.

R. S. Roth and A, D. Wads ley, (1964); Mixed Oxides of Titanium and

Niobium; The Crystal Structure of TiNb^^Ogg (TiOg • 12Nbg05 ) Acta Cryst.

(accepted)

.

R. S. Roth, A. D. Wadsley, and B. M, Gatehouse, (1964); Composition of

the Phases in the Systems NbOg - Nb^Og and TiOg - NbaO^; Naturwissenschaften _51, (11) .

R, S. Roth and J. L. Waring, (1964); Ixiolite and other Polymorphic

Types of FeNbO^ ; Am. Mineral., 49 (3-4), 242.

S. Rubin, (1964a); Standardization of Definitions for Hall Effect Devices; a talk delivered at the Rotating and Static Precision Components

Symposium, Washington, D. C. In April, and Published in the Proceedings

of the Symposium, printed by the Department of the Navy, Bureau of

Naval Weapons

.

S. Rubin, (1964b); Hall Generators, What, Why, and How Much; a talk

delevered at the IEEE International Convention, New York City, March

23, and published in the 1964 IEEE International Convention Record,

Instrumentation, pt. 8, 74.

S. Rubin and G. Rogers, (1964); Sensitivity Indices for Hall Generators;

1964 IEEE International Convention Record, Instrumentation, pt . 8, 74.

S. Ruthberg and L. Frankel, (1964); Dielectric Behavior of the FilmFormed on Mica Cleaved in Moist Air; J. Res. Natl. Bur. Std., 68A , 173.

J. F. Schooley, W. R. Hosier, and Marvin L. Cohen, (1964); Superconductivity in Semiconducting SrTiOg; Phys. Rev, Letters, J^, 474.

J. A. Simmons, R. L. Parker, and R. E. Howard, (1964); Theory of Whisker Growth and Evaporation; J. Appl. Phys., _35, 2271.

S. Spinner and J. B. Wachtman , Jr., (1964); Some Elastic Compliances of

Single Crystal Rutile from 25 °C to 1000 °C submitted to J. Res. Natl.

Bur. Std.

R. L. Streever and G. A. Uriano, (1964); Nuclear Magnetic Resonances

of ^^Ga and ''^Ga in Gallium-Substituted Yttrium-Iron Garnets; Phys.

Rev. Letters, J^, 614.

H. E. Swanson, M. C. Morris, E. H. Evans, and L. Ulmer, (1964); Standard X-Ray Diffraction Powder Patterns; Natl. Bur. Std. Monograph 25

Section 3.

L. J. Swartzendruber , (1964a); Correction Factor Tables for Four-Point

Probe Resistivity Measurements on Thin, Circular Semiconductor Samples;

Natl. Bur. Std, Technical Note 199.

L. J. Swartzendruber, (1964b); Calculation for Comparing Two-Point and

Four-Point Probe Resistivity Measurements on Rectangular Bar-Shaped

71
Semiconductor Samples; Natl. Bur. Std. Technical Note 241.

L. J. Swartzendruber , (1964c); Four-Point Probe Measurement of NonUniformities in Semiconductor Sheet Resistivity; Solid-State Electronics

7, 413.

J. L, Torgesen and J. Strassburger , (1964); Growth of Oxalic Acid

Single Crystals from Solution; Solvent Effects on Crystal Habit;

Science (accepted)

.

J, B. Wachtman, Jr. and L. R. Doyle, (1964); Internal Friction in

Rutile Containing Point Defects; Phys . Rev. 13 5A , 276.

J. L. Waring and R. S. Roth, (1964); Tetragonal Phases of the General

Type lOMgO^-gOMl 0^ , Apparently isostructural with Ta^Og • 2Nbg05

;

Acta Cryst". 17_, 455.

C. E. Weir and R. Schoeder, (1964); Infrared Spectra of Crystalline

Inorganic Borates; J. Res, Natl. Bur. Std., August, 1964.

72

<t U.S. GOVERNENT PRINTING OFFICE : 1964 O - 746-443