bluuebunny/crossref_metadata_2025 huggingface dataset:
Model for Switching and Polarization Reversal in Colemanite
Authors: Wieder H. H.
Published: April 2005

The characteristic properties of the displacement current transients obtained from ferroelectric colemanite crystals during polarization reversal are presented in detail. A phenomenological and semiempirical model of the switching mechanism is proposed. The model yields good agreement with the switching current dependence upon time, field amplitude and ambient temperature. It is based upon random nucleation followed by extensive sidewise displacement of the nucleated 180° domains. A model based upon three dimensional growth of nucleated domains is shown to be in poor agreement with experiment.
Variation in Ferroelectric Characteristics of Lead Zirconate Titanate Ceramics Due to Minor Chemical Modifications
Authors: Gerson Robert
Published: April 2005

Lead zirconate titanate ceramics with certain 3- or 5-valent additions (lanthanum, neodynium, tantalum, and niobium) are found to be characterized by low aging of electrical and mechanical properties, a well-defined hysteresis loop, and by high electrical and mechanical losses. Experimental investigations are reported on plain lead zirconate titanate and on a low-aging niobium modification.

The experiments included an electron microscope study of the ceramics and a number of electrical measurements. As a result of the study, the changed properties of the substituted material have been explained as being due to domain wall motion under low electric field. The results of electrical measurements supporting this conclusion, and a hypothesis accounting for the effects in terms of lattice vacancies, are presented.

The 3- or 5-valent additives described in the foregoing also cause greatly increased volume resistivity in the ceramic. This has not been satisfactorily explained.
Dislocation Structure and the Formation and Strength of Sodium Chloride Whiskers
Authors: Webb W. W.
Published: April 2005

Details of dislocation structure have been determined for a variety of NaCl whiskers and microcrystals grown from porous substrates moistened with supersaturated aqueous solution. Some of the smaller needle-like crystals have the single dislocation with an axial screw component usually assumed for whiskers. Larger whiskers and platelets often have much more complicated dislocation structures and may have higher dislocation densities than normal bulk crystals. Strengths were compared with dislocation structures and it was found that the nearly theoretical strengths observed in some of these whiskers are not due to merely a size effect but are directly related to the dislocation structure. Even crystals with high dislocation densities exhibited high strength in bending provided that all of the dislocations were so arrayed that they were not influenced by the applied stress. Regular dislocation arrays often occur naturally with this growth mechanism. However, irregular dislocation structures often associated with growth irregularities invariably resulted in low strength. Techniques for application of x-ray diffraction microscopy to determination of the dislocation structure of microcrystals are described.
Novel Mechanism for Mass Transport during Whisker Growth-Cesium Chloride from Aqueous Films
Authors: Webb W. W. , Bertolone N. P.
Published: April 2005

Capillary rise of a saturated solution within a hollow whisker has been found to provide a mechanism yielding growth at the tips of cesium chloride whiskers on a moist substrate in air at room temperature. The driving force for crystal growth is local supersaturation due to evaporation of water from solution at the tip of the capillary pore in each whisker. Screw dislocations provide the lattice steps on the whisker tips.
Outgassing Caused by Electron Bombardment of Glass
Authors: Todd B. Johnson , Lineweaver Jack L. , Kerr John T.
Published: April 2005

A flow system used for continuous measurement of the gases evolved from aluminized glass during bombardment with 20 kev electrons is described. The system is also suitable for gettering measurements. A cathode-ray tube containing the samples is sealed directly to the source of a mass spectrometer. Calibration of the first flow system built revealed the gettering of oxygen by the graphite-silicate conductive coating and the hot metal parts of the electron gun of the cathode-ray tube. This gettering was minimized in a second flow system. It was found that oxygen constitutes at least 95% of the gas evolved from each of five types of glasses investigated. Also, a graphite-silicate coating can play a dual role in a cathode-ray tube; when not bombarded by electrons it is an active getter for oxygen, but when bombarded it is a source of oxygen, carbon monoxide, and carbon dioxide.
Determination of Molecular Field Coefficients in Ferrimagnets
Authors: Rado G. T. , Folen V. J.
Published: April 2005

An improved method is presented for determining those three molecular field coefficients which yield essentially the best agreement between the Néel theory and the experimental curve of saturation moment per unit mass (σ) versus temperature (T) in a given ferrimagnetic material. This method is analytical, and for a given accuracy it is more rapid than previously used trial-and-error methods. Experimental data on σ vs T are presented for monocrystals of lithium ferrite and two compositions of magnesium-iron ferrite. One of the latter ferrites was measured in two states of ionic distribution which were obtained by varying the heat treatment. Application of the analytical method to these data shows that the agreement between the Néel theory and experiment is somewhat better than that expected on the basis of previous work. The present method is particularly useful for determining the temperature dependence of the sublattice magnetizations. Accurate values of these magnetizations are required, for example, in calculations of the temperature dependence of magnetocrystalline anisotropy by means of crystalline field theory.
Time-Dependent Electron Flow
Authors: Pease M. C.
Published: April 2005

The conditions of self-consistency for electron flow through arbitrary static or time-varying electric and magnetic fields are established assuming (a) nonrelativistic flow, (b) single streaming–i.e., the velocity has a single value and direction at every point, and (c) the electrons originate on a cathode not threaded by magnetic lines of force. In the case where the magnetic field is constant and uniform, a single-vector differential equation can be written which determines all possible solutions.

From this equation certain time-variant solutions are developed. These are fully self-consistent–that is, large signal–solutions which exhibit some of the nonlinear behavior that would be expected of such solutions.

Probably the most interesting of these solutions–since it offers an explanation of an observed phenomenon that does fit previous theory–is a radial oscillation of the cloud in a filamentary cathode smooth bore magnetron at ω/2.

The possible application of the other solutions to anomalous behavior in various magnetron type devices is also discussed.
Formation of Cesium Antimonide. I. Electrical Resistivity of the Film of Cesium-Antimony System
Authors: Miyake Kiyoshi
Published: April 2005

The films of Cs–Sb alloys whose compositions were determined by the weighing method, were prepared at the temperature ranged from 70°C to 100°C. The electrical resistance and its temperature dependency of the samples, of which atomic ratio of Cs to Sb was ranged from 0.91 to 4.86, were measured. The reproducibility of electrical resistance was obtained for all the samples, except for Cs3.30Sb, and the temperature coefficients of resistance of the samples, except for Cs0.91Sb, were all negative. It was found that three compounds, CsSb, Cs3Sb2, and Cs2Sb in addition to Cs3Sb, having a remarkably high resistance, could be formed. The observed values of the electrical resistivity at 0°C and the thermal activation energy associated with conductivity were 1.84×103 ohm-cm, 0.61 ev for Cs1.02Sb; 1.82×103 ohm-cm, 0.76 ev for Cs3.02Sb2; 2.85×103 ohm-cm, 0.62 ev for Cs2.02Sb; and 1.95×103 ohm-cm, 0.77 ev for Cs3.33Sb. The alloys with atomic ratio above 4 looked gold in reflected light, and those with atomic ratio above 5 were not formed.
Scattering by Nonspherical Particles
Authors: Greenberg J. Mayo
Published: April 2005

The small angle scattering approximation of Schiff is applied to several nonspherical body shapes. Effects of orientation and elongation are discussed.
Interaction between Arsenic and Aluminum in Germanium
Authors: McCaldin J. O.
Published: April 2005

The behavior of As in Ge containing regions doped with ∼5×1020/cc Al was studied. The solubility of As is enhanced tenfold or more by the heavy Al doping, on the basis of (1) measurements of conductivity type and (2) the negative results of a search for compounds by x-ray diffraction. The behavior of As diffusion fronts was studied by observing the progress of the p-n junction formed in Ge containing 1017/cc In. When a region of heavy Al doping was added, the p-n junction was displaced. The displacements indicate that the diffusing As is attracted to regions of heavy Al doping. These results are similar to those of Reiss, Fuller, and others for Li in Si, though a detailed understanding is not yet available in the present case.
Elastic Constants of Single Crystal Beryllium
Authors: Smith J. F. , Arbogast C. L.
Published: April 2005

The five independent elastic constants of beryllium have been determined with the pulse echo technique at a frequency of 10 Mc/sec. The values extrapolated to 0°K are C11=29.94±0.06, C33=34.22±0.12, C44=16.62±0.05, C12=2.76±0.08, C13=1.1±0.5 in units of 1011 dyne/cm2. Voigt averaging and Reuss averaging of the single crystal elastic constants give excellent agreement because of the small magnitude of the nondiagonal elements, C12 and C13. The averaged values compare favorably with previous data from polycrystalline beryllium.
Longitudinal Wave Propagation in Stretched Polymers
Authors: Mason Peter
Published: April 2005

The wave equation is derived for the propagation of longitudinal waves along a stretched filament of a highly elastic material. It is found that the tension in the filament reduces the effective modulus by twice the product of Poisson's ratio and the tensile traction, leaving the internal viscosity term unchanged. This result is illustrated by measurements of continuous 1 kcps wave propagation in natural rubber at 50°C, where the damping is small (tan δ<0.1). An alternative derivation is given for the purely elastic case of zero damping without restriction upon the amplitude.

The ``equilibrium'' or ``static'' Young's modulus is obtained for extensions up to about 600% from the slope of the equilibrium stress-strain curve and used to predict the corresponding wave velocities from the wave equation for zero damping. The predicted velocities are slightly higher—by up to about 10%—than the measured velocities. It is shown that the deviations could arise from differences in rate of strain between the wave-propagation and the stress-strain measurements. At the higher extensions the rubber is very hysteretic for large deformations, and the Young's modulus governing the small-amplitude wave propagation is shown to relate substantially to the loading branch of the stress-strain curve.
Density of a Thorium Monolayer for Maximum Thermionic Emission
Authors: Danforth W. E. , Goldwater D. L.
Published: April 2005

An investigation is described in which a high-sensitivity analytical balance of standard design is used for determination of the surface density of that thorium layer which corresponds to maximum thermionic emission with the thorium-on-tungsten system. Following Brattain and Becker's definition of this value of surface density as one ``f unit,'' thorium vapor is allowed to accumulate on a quartz plate until a weighable number of f units (about 600) has been deposited. The thorium flux in f units per minute is monitored periodically by means of a tungsten filament diode during the course of the deposition. Two polycrystalline specimens of ribbon from the same source have yielded the value of (4.2±0.2)1014 atoms/cm2 as the density for maximum emission. This is to be compared with a value of 5.0×1014 atoms/cm2 obtained in 1934 on theoretical grounds by Langmuir.
Growth of Cesium Chloride Crystals from Solution and Melt
Authors: Avakian P. , Smakula A.
Published: April 2005

Large cesium chloride crystals were obtained from solution only upon addition of urea. These crystals, however, show NH4+ impurity. Since CsCl undergoes a phase transition between its melting point and room temperature, normal growing methods from the melt could not be used, but a modified (``double-run'') Bridgman method yielded good results.
Propagation Constants for Electromagnetic Waves in Weakly Ionized, Dry Air
Authors: Phelps A. V.
Published: April 2005

Formulas and graphs are given for the calculation of the propagation constants of an electromagnetic wave in weakly ionized, dry air at ionospheric temperatures in the presence of a magnetic field. Experimental studies of electron collision frequencies in nitrogen and oxygen are reviewed and used to obtain the magnitude and energy dependence of the electron collision frequency in air. The equations for the components of the conductivity tensor are developed taking into account the approximately linear dependence of the electron collision frequency on electron energy. Expressions derived on this assumption are found to be accurate except at low temperatures, high pressures, and low frequencies. The errors resulting from the use of an effective value for the energy independent collision frequency in the Appleton-Hartree equations are evaluated. Procedures are given for the calculation of the propagation constants for electromagnetic waves propagated parallel to and perpendicular to the magnetic field. These results are then applied to the derivation of relations required to reanalyze the ionospheric collision frequency measurements reported by Kane. The use of an effective collision frequency is found to lead to errors comparable to the experimental errors in the ionospheric observations.
Effects of Internal Oxidation and Heat Treatment on the Electrical Resistivity of Dilute CuMn, CuFe, and CuCo Alloys
Authors: Domenicali C. A. , Christenson E. L.
Published: April 2005

This investigation was concerned with the effects of high temperature treatment in vacuo or in rarefied oxygen atmospheres upon the effective electrical resistivity of dilute (copper-rich) CuMn, CuFe, and CuCo rods and wires. The CuMn alloys studied most extensively contained between 1 and 12 at. % manganese while the CuFe and CuCo alloys contained between 0.1 and 0.3 at. % iron or cobalt. It was found that the solutes in the CuFe and CuCo wires and rods become rapidly oxidized (internally) during heat treatment for several hours at 990°C in pure oxygen pressures of 0.5 μ or greater, while in 0.05 μ O2 this oxidation is absent and previously oxidized specimens are reduced. These observations are based on measurements of electrical resistivity, and in the case of CuFe, substantiated by measurements on the magnetization. Heat treatment of these CuFe and CuCo wires and rods near 1000°C for several hours either in vacuo (0.1 μ air) or 5 μ O2 does not appreciably affect the cross-sectional uniformity of these specimens. In the case of CuFe alloys, the magnetic behavior demonstrates the virtually complete oxidation of solute to Fe3O4 after prolonged anneal in an oxidizing atmosphere. The behavior of the CuMn alloys was found to be more complicated, partly because of the high solute concentrations involved. It was found that wires and rods of CuMn rapidly become nonuniform in solute concentration throughout their cross section when annealed near 1000°C for several hours either in a vacuum (0.1 μ air) or in 5 μ of pure oxygen; this nonuniformity of manganese concentration develops at a considerably higher rate in the 5 μ O2 atmosphere than in vacuum, and leads to erroneous values of the resistivity and to erroneous curves of resistivity vs temperature for CuMn wires or rods. On the other hand, annealing of such wires for several hours in vacuum at temperatures around 800°C does not appreciably disturb the cross-sectional uniformity. Finally, it is emphasized that the ``carrier gas'' technique (involving a flow system with small concentrations of oxygen mixed with helium at atmospheric pressure, for example) is entirely unsatisfactory for experiments on internal oxidation, particularly if one wants to know the oxygen partial pressure.
An Improved Method of Growing CdS Crystals from the Vapor Phase
Authors: Fochs P. D.
Published: April 2005

The gradual increase in the difference in temperatures of two Kanthal heating elements enables CdS crystals to be grown directly on the inside of a silica tube, remote from one another, instead of on a continuous polycrystalline CdS substrate as happens in most existing methods.
Grain-Boundary Photoresponse
Authors: Lindemann W. W. , Mueller R. K.
Published: April 2005

Measurements of the sensitivity of grain-boundary photodetectors indicate an expected minimum detectable power of better than 10−14 w. Major factors governing the sensitivity are the minority carrier lifetime and the distance of the boundary from the irradiated surface. Spectral measurements show an added absorption edge response at about 1.67 μ and 1.72 μ. This added response could be caused by deep-lying acceptor levels or by excitons with a long lifetime. However, the experimental evidence points to direct absorption at the grain boundary as the most likely reason for the absorption edge irregularities.
Surface Space-Charge Calculations for Semiconductors
Authors: Frankl D. R.
Published: April 2005

Approximation formulas for the surface excesses of carriers at large values of the reduced surface and bulk potentials are derived, and computed results are presented.
Oblique-Incidence Anisotropy in Evaporated Permalloy Films
Authors: Smith D. O. , Cohen M. S. , Weiss G. P.
Published: April 2005

Magnetic anisotropy has been observed in evaporated Permalloy films deposited at oblique incidence of the vapor. Electron micrographs of such films reveal chains of crystallites whose long axes are oriented perpendicular to the vapor beam. A ``self-shadowing'' model is proposed to explain chain growth, i.e., the area behind a crystallite is left vacant because it is in the crystallite's shadow. Oriented crystallite chains are thus caused by a purely geometric process; their existence has also been demonstrated for Au, Pt, W, and Mg. Oriented chains give rise to a number of macroscopic effects: magnetic anisotropy, anisotropic resistance, dichroism, and anisotropic resonance linewidth. Experiments involving the stripping of oblique-incidence Permalloy films from their substrates indicate the presence of an anisotropic strain which, in conjunction with magnetostriction, gives another contribution to the magnetic anisotropy; this contribution explains the observed compositional dependence of the magnetic anisotropy. Surface tension, which tends to contract the crystallite chains, is postulated as the generating force of anisotropic strain; surface tension could similarly generate the isotropic strain which is found in normal-incidence films.
Hall Field Relaxation in Semiconductors at High Frequency
Authors: Champlin Keith S.
Published: April 2005

Using a simple extension of standard magneto-ionic theory, the frequency dependence of the complex Hall field is calculated for samples with rectangular, cylindrical, and spherical geometry. The result has application to ``open-circuit'' Hall effect measurements on semiconductors at microwave frequencies.
Fast Neutron Bombardment of Germanium and Silicon Esaki Diodes
Authors: Easley J. W. , Blair R. R.
Published: April 2005

The fast neutron irradiation behavior of germanium and silicon Esaki diodes has been experimentally examined. The dominant change produced is an increase in the ``excess'' current which is proportional to integrated neutron flux. The observed increase in the vicinity of the current minimum is approximately 2.6×10−15 amp/fast neutron and 1.1×10−14 amp/fast neutron for germanium and silicon diodes respectively. Substantial changes result in the voltage-current characteristics of the diodes employed in the decade of exposure between 1016–1017 fast neutrons/cm2 for germanium diodes and between 1015–1016 fast neutrons/cm2 for silicon diodes. One kilomegacycle cavity oscillators employing germanium diodes exhibit a marked reduction in power output in the decade of exposure between 1016–1017 fast neutrons/cm2. The magnitude of the decrease is in approximate agreement with the observed bombardment reduction of diode negative conductance.
Interaction between High-Power Microwave Losses and Magnetic Flux Reversal
Authors: Gyorgy E. M. , Hagedorn F. B.
Published: April 2005

The off-resonance microwave absorption (subsidiary absorption) which frequently occurs at high-microwave power and which may exist even in the absence of an external dc magnetic field has been used to observe the interaction between the magnetic flux reversal and the microwave loss processes in polycrystalline ferrite. These experiments have shown that the spin waves associated with high-power, off-resonance microwave absorption have a negligible effect on the flux reversal process. However, the flux reversal process has a marked effect on the high-power microwave loss. During the flux reversal process, this high-power, off-resonance microwave absorption was found in some cases to be negligible.
Effect of Thermal History on the Dislocation Substructure near the Surfaces of a Lithium Fluoride Crystal
Authors: Schultz J. M. , Washburn J.
Published: April 2005

A series of x ray and etch pit experiments has been performed to determine some of the effects of temperature on the perfection of surface layers in LiF. It was found that the perfection of a cleaved surface is substantially increased at temperatures near the melting point, that rearrangement and annihilation of dislocations takes place at much lower temperatures, and that rapid cooling promotes the formation of shallow dislocation loops.
Electron Sheet Beam Focusing with Tape Ladder Lines
Authors: Waters William E.
Published: April 2005

The dc properties of a periodic focusing system consisting of a parallel pair of ladder lines, together with focusing plates parallel to the lines, are calculated. First, Laplace's equation is solved in an approximate way; following this, the paraxial-ray equation for an electron sheet beam, injected into the system halfway between the ladder lines, is solved for perveance, plasma frequency, beam stiffness, and average beam potential. Finally, a numerical example is presented and discussed.
NMR Absorption in Teflon Fibers
Authors: Hyndman D. , Origlio G. F.
Published: April 2005

Nuclear magnetic resonance absorption in oriented polytetrafluoroethylene fibers has been investigated in the temperature range 170°–380°K. The sample, in the form of a parallel bundle of fibers, showed a marked dependence of line shape on the direction of the applied magnetic field over the temperature range studied, although the observed anisotropy was much greater above 285°K than below. Changes occurring in the linewidth and second moment at around 285°K indicate a rotational disorder transition in the crystalline regions of the polymer, and serve to illustrate the advantages of using oriented fibers in the NMR investigation of semicrystalline polymers.
Experimental Study of Thermal Diffusion in Dilute Solutions of High Polymers
Authors: Whitmore Frank C.
Published: April 2005

Ham [J. Appl. Phys. 31, 1853 (1960) (preceding paper)] has derived a simplified theory for thermal diffusion in dilute solutions of high polymers. It is of interest to apply this theory to two different types of polymer solutions: (a) dilute solutions in a good solvent, and (b) dilute solutions in a poor solvent. By studies of the concentration, temperature, and molecular weight dependence of the thermal diffusion ratio in these two different types of polymer solutions, it has been possible to obtain a detailed test of the theory.
Effect of Temperature and Reactor Irradiation on the Strength of Biaxially Oriented Polyethylene Terephthalate
Authors: Haynes A. , Hsiao C. C.
Published: April 2005

Samples of biaxially oriented polyethylene terephthalate irradiated in a nuclear reactor have been investigated at five temperature levels ranging from − 150°F to 350°F. In general, from tensile studies, the ultimate tensile strength was found to decrease markedly to a relatively low magnitude upon receiving a reactor irradiation dose having a thermal neutron bombardment component of 1018 nvt and over. The modulus of elasticity for both the irradiated and nonirradiated samples was found to increase with the decrease of the temperature.

The fracture surfaces of the biaxially oriented polyethylene terephthalate samples obtained at − 15°F are also recorded for reference.
Photographic Light Scattering by Polyethylene Films
Authors: Stein Richard S. , Rhodes Marion B.
Published: April 2005

The photographic light scattering technique permits a measurement of the size, anisotropy, radial periodicity, packing, and internal structure of polymer spherulites. The theory of some of these effects is described, and experiments are presented showing changes occurring in the melting and growth of spherulites.
Time and Temperature Dependence of the Ultimate Properties of an SBR Rubber at Constant Elongations
Authors: Smith Thor L. , Stedry Paul J.
Published: April 2005

The ultimate properties of amorphous rubbers at temperatures above Tg are considered in terms of stress-strain curves to rupture measured at different strain rates and temperatures. The consideration indicates that a specimen held at a fixed elongation should break eventually, provided the elongation exceeds a critical value. This expected behavior was found by studying an SBR rubber. For samples maintained at different elongations for up to seven days, both the time to break and the stress at break were measured at eight temperatures from 1.7° to 60°C. For comparison, the ultimate properties were also measured at different strain rates and temperatures. The comparison indicates that for a given ultimate elongation and stress at break, the time to break under conditions of constant elongation is less than under conditions of constant strain rate.
Hollow Pyramidal Crystals of Polyethylene and a Mechanism of Growth
Authors: Niegisch Walter D. , Swan Paul R.
Published: April 2005

A hollow pyramidal model for diamond-shaped single crystals of polyethylene is proposed which accounts for the electron microscope observations and electron diffraction effects presented in this paper and in the literature. The pyramidal shape occurs because the rows of folded molecules along the (110) growth face in each quadrant of the crystal are translated along the molecular chain direction by two carbon-carbon distances relative to the previous row. This translation presumably occurs in order to relieve steric interferences at the folds or loops of the polymer chain. The resulting triclinic cell, of which the familiar orthorhombic cell is in reality a subcell, has a c̄ dimension equal to the constant fold length of the polymer chain, and remaining parameters of ā=7.84 A, b̄=5.56 A, α=(90−27.3)°, β=(90−19.0)° and γ=81.5°. The values 19.0 and 27.3 degrees are, respectively, arctan (c/a) and arctan (c/b) of the orthorhombic subcell, so that the (001) planes of the triclinic cell which contain the folds on the surface of the pyramids are (111) planes relative to the orthorhombic subcell.
Wave Functions and Energy Eigenvalues for the Polytetrafluoroethylene Chain
Authors: Pao Yoh-Han , Bjorklund R. F.
Published: April 2005

The paper reports on a quantum mechanical investigation of an isolated polytetrafluoroethylene molecule. The purpose of this investigation is twofold: to find the energy gap between filled and empty electronic bands and to determine the energy required to change the conformation of the molecule. For reasons of simplicity, the carbon atoms are assumed to have the planar zigzag conformation in the ground state of the molecule. Molecular wave functions are constructed from Bloch sums taken along the four rows of fluorine atoms. The basis functions used are Gaussian approximations to 2p and 3s atomic orbitals. The suitability of this choice is tested in a preliminary calculation of the dissociation energy of the hydrogen fluoride molecule.

In polytetrafluoroethylene, the molecular orbitals form bands. The energy gap between the filled 2p band and the empty 3s band is calculated as 10.07 ev, suggesting negligible intrinsic semiconduction. The width of the 2p band is 0.0625 ev, signifying that chain conformation may change easily at room temperature, for example from a right-handed helical conformation to the conformation of the opposite hand.
Chain Folding and Free Energy Density in Polymer Crystals
Authors: Peterlin Anton
Published: April 2005

Macromolecular chains in freely growing crystals very likely fold back at regular intervals in order to minimize the free energy density of the crystal. The surface energy contribution favors infinite thickness. The smearing out effect of interchain potential field, however, arising from the incoherent part of fluctuation of neighboring chains and increasing with the fold period, favors thin crystals. For sake of simplicity the longitudinal chain vibrations were considered in spite of the fact that in actual crystals the main contribution most likely comes from rotational oscillations. Since the general character of smearing out effect is nearly the same in both cases the present results may be applied at least qualitatively. They fairly well represent the general trend of temperature dependence of polymer crystal thickness and its change with intermolecular forces.
Anomalous Hall Effect in AgSbTe2
Authors: Wolfe R. , Wernick J. H. , Haszko S. E.
Published: April 2005

The Hall coefficient of the ternary semiconductor AgSbTe2 near room temperature is positive in some specimens and negative in others, although the Seebeck coefficient is always positive. The negative Hall coefficient decreases as the temperature is lowered from 180°K to 70°K and changes sign in lower temperatures. This negative Hall coefficient is associated with the presence in the AgSbTe2 of a second phase consisting of Ag2Te. The properties of the two-phase material are interpreted in terms of the theory of the transport properties of inhomogeneous semiconductors. In single-phase AgSbTe2 containing 3×1019 holes per cm3, the hole mobility is 35 cm2/v sec at 300°K and it varies approximately as T−0.5. {Note added in proof. It has been suggested by Armstrong, Faust, and Tiller [J. Appl. Phys. 31, 1954 (1960)] that the pattern in Fig. 3(a) is associated with the presence of Sb2Te3 as a Widmanstätten precipitate along {111} planes in the AgSbTe2. This would indicate that none of the material was single phase. Even though the Sb2Te3 in the measured specimens is present in quantities too small to be detected in our x-ray powder photographs, it may have some effect on the measured properties. Therefore, the electrical properties of single-phase AgSbTe2 have yet to be determined.} The lattice thermal conductivity is so low (0.0064 watts/cm°C at 290°K) that the calculated ``phonon mean free path'' is less than the nearest neighbor distance. The thermal conductivity of a specimen rich in AgSbTe2–Ag2Te eutectic is higher than that of either of the components. This excess thermal conductivity is attributed to circulating thermoelectric currents.
Diffusion of Ag+, Cl−, and Cd++ in Silver Chloride Single Crystals
Authors: Reade Richard F. , Martin Don S.
Published: April 2005

The diffusion rates of silver, chlorine, and cadmium ions in single crystals of silver chloride have been investigated by means of a modification of the surface counting method. The diffusion coefficient of the silver ion from 200° to 400°C was represented by the equation D=9.36 exp(−1.01 ev/kT) cm2/sec. Estimates of chloride ion activation energies gave a value of 1.57 ev between 350° and 400°C, and a value of 0.37 ev below 280°C. The silver and chloride ion diffusion data have been compared with results of workers who used sectioning methods. The diffusion coefficient of the cadmium ion may be expressed by the equation D=32.8 exp(−1.36 ev/kT) cm2/sec+2.35×10−5 exp(−0.56/kT) cm2 sec.
Measurement of Orientation in Polypropylene Film
Authors: Wilchinsky Zigmond W.
Published: April 2005

An average fiber axis orientation in polypropylene film was measured quantitatively from x-ray diffraction determination of orientation of two planes containing this axis. This orientation was expressed as the average square cosine of the angle between the fiber axis and a chosen reference direction in the sample. It was necessary to use an indirect method since there are no crystal planes perpendicular to the fiber axis. The nature of the fiber axis orientation thus determined was found to be consistent with birefringence measurements and qualitative deductions from pole figures. Films produced by flat die extrusion showed a double orientation in which the fiber axis is preferentially oriented in the extrusion direction, and the (010) crystal face is parallel to the film surface. Both components of the orientation tended to be of the same magnitude.
Effect of Magnetic Fields on Thermionic Power Generators
Authors: Schock Alfred
Published: April 2005

It is demonstrated that the high currents present in large thermionic power generators produce magnetic fields which result in a considerable reduction of electron transmission and energy conversion efficiency. To overcome the adverse effect of the self-induced field, the report presents the concept of a magnetothermionic power generator, employing an externally produced magnetic field parallel to the current direction. Analysis indicates that this concept will permit efficient operation of large generators. In addition, by use of a modulated field coil current, it offers the possibility of the direct generation of alternating current, at a controlled frequency.
Temperature Dependence of the Debye Temperatures of Aluminum, Lead, and Beta Brass by an X-Ray Method
Authors: Chipman D. R.
Published: April 2005

The temperature dependence of the Debye temperature of aluminum, lead, and beta brass was determined by measuring the integrated intensity of a high angle x-ray diffraction peak from each of the materials as a function of temperature. This measured temperature dependence agrees well with the corresponding function obtained from elastic constant data, although it is determined by much higher lattice frequencies. In agreement with the elastic constant measurements, evidence is found for an explicit temperature dependence beyond that resulting from the simple dependence of Debye temperature on volume.
Hole Mobility and Crystal Size in Lead Sulfide Photoconductive Films
Authors: Spencer H. E. , Morgan J. V.
Published: April 2005

A correlation has been found between the size of the microcrystals in photoconductive lead sulfide films and hole mobility calculated from Hall, signal, and noise measurements. Films composed of larger microcrystals exhibit larger mobilities. Field-effect mobility as a function of frequency has also been measured. The data indicate that the surfaces as well as the bulk of the films are p type. The lead sulfide-air interface of the films changes from exhaustion type to enhancement type as the film thickness increases.
Conservation Laws of an Interacting Electron Beam
Authors: Pease Marshall C.
Published: April 2005

The linearized theory of electron beams interacting with a circuit is studied. Such systems may be considered as coupling the modes of, for example, the beam and the circuit. It has been found, previously, that if these modes are properly defined, then there is a conservation law which states the constancy of the total power in these individual modes, independent of the extent of coupling. In single-frequency beam-type devices, this conservation law is Chu's kinetic power theorem. In multiple-frequency parametric systems, it is the linearized Manley-Rowe relation. The problem of such an interpretation is to determine what is an appropriate modal description that will lead to a convenient and useful conservation law. To obtain a systematic means of finding such a representation, we observe that any linear homogeneous system with n degrees of freedom has n quadratic invariances. The kinetic power theorem and the linearized Manley-Rowe relation are examples of such quadratic invariances, which are distinguished from the others by being independent of certain of the parameters of the system. Methods are obtained for determining, from the differential equations of the system expressed in any appropriate variables, the quadratic invariance, if it exists, which is independent of a given parameter. If the basis is now changed to one which diagonalizes this invariance, then we will have determined a modal, or wave, description in terms of which the invariance becomes a kinetic power law, as it is usually written. This method of analysis is illustrated by application to the infinite-plane parallel beam, the interaction of a longitudinal thin beam with an incompletely coupled circuit, and the interaction of a weakly constrained filamentary beam with a transverse-field circuit.
Secondary Electron Emission of MgO Crystals Bombarded by Relativistic Electrons
Authors: Pomerantz Martin A. , Shatas Romas A. , Schieve William C.
Published: April 2005

The yield of single crystals of MgO has been determined at a primary energy of 1.3 Mev, utilizing a modification of the ``sandwich'' technique developed earlier for investigating the secondary electron emission of metals at high primary energies. The value of δ for Al was measured concurrently under identical conditions.

The accumulation of surface charges usually encountered with insulators is prevented by the bombardment-induced conductivity of MgO. The influence of multiple scattering and energy loss of the primary beam, as well as of δ-ray production, must be considered when the targets are relatively thick as in the present case. An empirical correction for normalizing the thick target measurements to thin target conditions was determined.

The result is: δMgO=0.09±0.02 as compared with δAl=0.023±0.003.
Growth from the Melt. Part II. Cellular Interface Morphology
Authors: Bolling G. F. , Tiller W. A.
Published: April 2005

The microscopic shape of a solid-liquid interface has been examined theoretically for those growth conditions which give rise to a cellular morphology. The method of obtaining a general solution is set forth, and approximate treatments are used to compare the theoretical approach with experimental data. The variation of cell size with temperature gradients, growth velocity, stirring in the liquid, interfacial free energy, and solute content is examined, and the conditions governing the stability of a cellular interface compared to that of a smooth interface are predicted.
Determination of Streaming Velocity and the Flow of Heat and Mass in High-Current Arcs
Authors: Reed T. B.
Published: April 2005

Arc plasma streaming velocities were calculated from previously unpublished experimental data obtained by H. N. Olsen on total pressure distributions at the anodes in 100- to 300-amp argon and helium arcs. The dynamic streaming component of pressure was calculated by subtracting the magnetic component (due to the self-magnetic field of the arc) from this total pressure. Arc temperatures also measured by Olsen were then used to calculate densities and heat contents of the plasma, and these were used with the streaming pressure to calculate velocities and mass and heat flow distributions. These in turn were integrated to give total mass and heat flows. The results compare reasonably with other measurements and estimates in the literature. Peak velocities range from 16 000 to 60 000 cm/sec, mass flows from 0.04 to 0.23 g/sec. The plasma heat flow distribution shows a close similarity in shape to values of heat transfer intensity at the anode measured by O. H. Nestor. A comparison of the total heat flow in the plasma to the total heat transfer due to streaming at a series of currents shows heat transfer proportional to (heat flow)0.62 which agrees with correlations used for heat transfer from gases and flames. A simplified model of arc pumping is presented which suggests that heat and mass flow should increase as (current)32. A simple analog experiment in mercury is described which illustrates graphically the streaming caused by a divergent current path in a conductor.
On the Incorporation of Neodymium in Mixed Yttrium-Neodymium-Iron Garnets
Authors: Goldring G. , Schieber M. , Vager Z.
Published: April 2005

The preparation and saturation magnetization of yttrium-iron garnets containing various amounts of neodymium was investigated. The amount of Nd which can be incorporated in the garnet structure was determined crystallographically and magnetically. The chemical analysis of the Nd/Y ratio was carried out by the counting of the characteristic x rays of Nd produced by proton bombardment in a Van de Graaff accelerator. A compound with a formula of YNd2Fe5O12 was found to be the richest iron garnet containing Nd and has a saturation magnetization, at room temperature, of 4.25±0.13 Bohr magnetons per formula weight compared to that of 3.55±0.13 of Y3Fe5O12 or Sm3Fe5O12.
Recent Appearance Potential Measurements Using an Electrostatic Electron Selector
Authors: Kerwin Larkin , Marmet Paul
Published: April 2005

The general principles of measuring appearance potentials by the electron bombardment method are reviewed. Recent improvements in the design of an electrostatic electron selector so as to improve the electron bombardment technique are described. The new instrument provides an electron beam with an energy spread of less than 50 mv. By means of it, measurements have been made on the vibrational levels N2+ and H2+.
Photoemission and Related Properties of the Alkali-Antimonides
Authors: Spicer William E.
Published: April 2005

The photoemissive process in the semiconducting alkali-antimonides is examined and values are given for the band gaps and electron affinities. The high photoelectric efficiencies of these materials are attributed to the ability of the excited electrons to traverse relatively large distances (250 A) without overwhelming energy losses, rather than to negligibly small electron affinities. The efficiency is found to be strongly dependent on the percentage of the electrons which are excited into states above the vacuum level. The properties of these materials depend to a large extent on the crystal structure. Cs3Sb and Na2KSb have a cubic structure, are p type, and seem to have a relatively simple valence band structure. K3Sb and Na3Sb have hexagonal crystal structures, are n type, and seem to have a relatively complex valence band structure. The evidence for an effect of band bending on the photoemission is considered.
Oxygen on Nickel
Authors: Germer L. H. , Hartman C. D.
Published: April 2005

Low-energy electron diffraction, with the diffracted electrons post-accelerated and observed on a fluorescent screen, has been used to study the adsorption of oxygen on a (100) face of a nickel crystal. Upon admitting oxygen to a clean face at room temperature, or at elevated temperatures up to 350°C, the first adsorbed atoms are arranged in narrow bands parallel to [110] directions on the crystal surface. Within one of these bands, atoms lie on lines at right angles to the band; these lines have a uniform separation of 4.98 A, but the atoms along each line are somewhat randomly spaced in multiples of the nickel spacing of 2.49 A. With further oxygen exposure (30×10−6 mm Hg sec) sufficient to produce half of a monolayer (one oxygen atom for every four surface nickel atoms), the arrangement is very chaotic unless the crystal has been heated, but after heating the arrangement is a simple square array with edge of 4.98 A. Further exposure to oxygen (100×10−6 mm sec) will produce a full monolayer consisting of this same square array with an additional oxygen atom at the center of each square. With still further exposure, oxygen, at least in part as physisorbed molecules, is piled on top of this first monolayer of atoms, the added molecules forming an array with square symmetry and edges parallel to the edges of the square array of surface nickel atoms. At least several layers of oxygen molecules can be adsorbed and are not removed by pumping at room temperature. Heating at 350°C removes a great deal of the adsorbed oxygen, and the structure of the remainder agrees with that of NiO having the orientation of the nickel crystal. This oxide is removed at 830°C, and the first layer of oxygen atoms at 880°C.
Potential Distributions in a Low-Pressure Thermionic Converter
Authors: Auer Peter L.
Published: April 2005

A plane diode model of a low-pressure cesium-filled thermionic converter is treated. It is assumed that all ions and electrons are created at the surface of the hot cathode with a Maxwellian distribution corresponding to the cathode temperature. The charged species are then assumed to move through the plasma, consisting of electrons, ions, and neutral cesium atoms, as free particles under the influence of their mutual space charge field. A method is outlined by which the potential distributions corresponding to different operating conditions may be calculated completely. In this fashion the operating characteristics of the converter may be related to the self-consistent space charge potentials. Instabilities as possible sources of tube oscillations are briefly discussed.
Bounds on Low-Energy Scattering Parameters
Authors: Spruch Larry , Rosenberg Leonard
Published: April 2005

Some recent results that determine an upper bound on the scattering length, whether or not composite bound states exist, are reviewed. The extension to the determination of an upper bound on (−k cotη)−1, where only one channel is open, is presented; the method used requires that the potential vanish identically beyond some given point. The results are applicable to the scattering of one compound system by another. Possible extensions and improvements of the method are discussed.
New Complex Phase in the Copper-Gold System
Authors: Scott R. E.
Published: April 2005

At the composition 31.6 at. % gold, the equilibrium diagram shows a two-phase mixture of ordered and disordered material extending from 320°C to 350°C. However, a long anneal in this interval results in an x-ray pattern showing superstructure reflections with strong satellites. The satellite pattern is obtained both by lowering and raising the temperature, and hence is believed to represent an equilibrium structure. The satellite pattern is interpreted in terms of a Cu3Au II type structure, which is derived from the ordered Cu3Au I by introducing antiphase domain displacements (a2+a3)/2 at regular intervals along the a1 axis, exactly analogous to the development of CuAu II from CuAu I. At 31.6 at. % gold, the period is 18a1 (9 a1 between consecutive domain boundaries). Between 320°C and 335°C, there is a two-phase mixture of Cu3Au I and Cu3Au II. From 335°C to about 345°C the structure is that of Cu3Au II. From about 345°C to 350°C there is probably a two-phase mixture of Cu3Au II and disordered material, but this has not been established. The satellite pattern is also obtained at the composition 29.2 at. % gold, and it is likely that the Cu3Au II type structure exists over a range of compositions on the gold rich side of Cu3Au.