NASA CR-1 34599

.Aft

ALKALI OXIDE-TANTALUM OXIDE AND ALKALI OXIDE-NIOBIUM OXIDE IONIC CONDUCTORS

by

R. S. Roth, H. S. Parker, W. S. Brower and D. Minor

prepared for

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

CONTRACT C-29933C

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D.C. 20234

1 1 Report No. CR-134599

2. Government Accession No. 3. Recioient's Catalog No. NBSIR 7L-LL0

A Tit I a t r-v /-4 Ci it^titla H. 1 iiie ana oudiiti6 ALKALI OXIDE-TANTALUM OXIDE AND ALKALI OXIDE-NIOBIUM OXIDE

IONIC CONDUCTORS

5. Report Date April 1974

6. Performing Organisation Code

7. Author(s) R. S. Roth, H. s. Parker, W. S. Brower and D. Minor

8. Performing Organization Report No.

10. Work Unit No. YOK 5650 9. Performing Organization Name and Address National Bureau of Standards

Washington, D.C. 20234

11. Contract or Grant No. C-29933C

13. Type of Report and Period Covered Final Report

October 1972 - October 1973

12. Sponsoring Agency Name and Address National Aeronautics and Space Administration

Lewis Research Center

21000 Brookpark Road

Cleveland, Ohio 44135

14. Sponsoring Agency Code

15. Supplementary Notes Project Manager: Patricia O'Donnell

16. AbstractA search was made for new cationic conducting phases in alkali-tantalate and niobate

systems. The phase equilibrium diagrams were constructed for the six binary systems

^'^2°5"-^^^'^°3' Nb^O^-NaNbO^, Nb^O^-KNbO^, Ta^O^-NaTaO^ , Ta^O^-LiTaO^ and Ta^O^-KTaO^.

Various other binary and ternary systems were also examined. Pellets of nineteen phases

were evaulated <by the sponsoring agency) by dielectric loss measurements. Attempts were

made to grow large crystals of eight different phases. The system Ta^O^-KTaO., contains

2 5 3 at least three phases which showed peaks in dielectffj-c loss vs. temperature. All three

contain structures related to the tungsten bronjzies with alkali ions in non-stoichiometric

crystallographic positions.

17. Key Words (Suggested by Author(s)) Alkali ions

Ionic conductors

Niobates

Tantalates

18, Distribution Statement Unclassified, Unlimited

19. Security Classif. (of this report) Unclassified

20. Security Classif. (of this page) Unclassified

21. No. of Pages 59

22. Price*

' For sale by the National Technical Information Service, Springfield, Virginia 22151

TABLE OF CONTENTS

SUMMARY 2 INTRODUCTION .... 3 DISCUSSION OF RESULTS

The System NL- O^-LiNbO^ 4

2 5 3 The System Ta^O^-LiTaO^ 4 2d 3 The System Nb^O^-NaNbO^ 5 The System Ta^O^-NaTaO^ 6

The System Nb^O^-KNbO^ 6

2 5 3 The System Ta^O^-KTaO^ , 7 Other Systems 8

Polycrystalline Specimen Preparation 9

Crystal Growth , 10

Nb^O^-KNbO^ 11

i2K^O:88Nb^O^ 11

2 2 5 17.5K^O:82.5Nb^O^ 12

2 2 5 Ta^O^rKTaO^ 12

Ta^O^:LiTaO^ System 12

2 5 3 IJb^O^-NaNbO^ System 13

Ta^O^-NaTaO^ System 13

Structural Mechanisms of Non-Stoichiometry in AlkaliNiobates and Tantales , 13

HTB 14

TTB 15

GTB 15

TTBs 16

Other Phases 17

SUMMARY OF RESULTS 18

FUTURE WORK 19

REFERENCES 20

FIGURE CAPTIONS 22

TABLES OF EXPERIMENTAL DATA 34

DISTRIBUTION LIST 53

1
SUMMARY

This report summarizes work carried out between October 1972 and

October 1973 under an agreement with the National Aeronautics and Space

Administration, Lewis Research Center (Interagency Order C-29933-C) to

study the phase equilibria of alkali oxide-tantalum and niobixam oxide

systems and synthesis of phases which might have interesting ionic

conductivity.

The phase equilibrium relations of six systems were investigated in

detail. These consisted of lithium, sodium and potassium tantalate, and

niobate with the corresponding tantalum and niobium oxide. In addition,

various other binary and ternary systems involving alkali oxides were

examined in lesser detail. In all, thirteen phases were found to contain

structures of sufficient interest to warrant further investigation. Nineteen

phases were prepared as solid pellets and transmitted to LeRC for evaluation

by dielectric loss measurement. Attempts were made to grow eight different

phases as large single crystals, and two were submitted to LeRC for evaluation.

In terms of ionic conductivity, the most interesting phases from

a structural point of view are those containing large tunnels only

partially occupied by alkali ions. The potassium tantalate system contained

four such phases, designated GTB, TTBs , HTB, and TTB (see table 6 for

meaning of these initials) . In all cases, the TB refers to a tungsten

bronze type structure. Those phases which exhibit a maximum in the dielectric loss vs. temperature curves proved to be high temperature phases

which are generally metastable at room temperature and do not have favorable melting characteristics for crystal growth directly from the melt.

In the coming year efforts will be expanded to include rubidium

systems as well as antimonates and mixed tantaliam-tungstates , in an effort to isolate an ionic conducting phase with favorable crystal

growth possiblities

.

2
INTRODUCTION

In the search for new ionic conductors, compounds in oxide systems

need to be examined, for structure types where packing of the complex ions

of the skeletal structure has the potential to produce loosely bound

alkali ions.

The compounds of alkali oxides with tantalum oxide and with niobium

oxide represent a class of such materials. The program siimmarized

in this report involved the investigation of the £)hase diagrams to

determine the phases which are actually contained in these systems

and to define selected phases of potential interest as solid ionic

conductors. Subsequent to this determination specimens were prepared

of single phase polycrystalline ceramic pellets for screening

measurements and, finally, attempts were made to grow single crystals

of those materials which appeared most interesting and feasible.

All the phases encountered were identified by single crystal x-ray

diffraction patterns and/or identity with previously reported structures.

For fast ion transport, it is probably advantageous to have an alkali

ion in a "non-stoichiometric" crystallographic position. For commerical

utilization of ionic conductivity, it is necessary to limit systems to

those which will contain little or no electronic conductivity and,

therefore, do not contain an element which is easily reduced during the

synthesis. The Ta"^^ ion is apparently very difficult to reduce [1],

and thus is ideally suitable as a host lattice for alkali "superionic-conductivity". Some preliminary work on alkali tantalate and niobate

systems has been previously summarized by the present authors [2] . A

complete detailed analysis of these system.s is presently being prepared

for publication and will be submitted to the Journal of Solid State

Chemistry in the near future [3, 4, 5, 6]

.

.3
DISCUSSION OF RESULTS

The System Nb^G^-LiNbO-,

A phase equilibrium diagram for the system Li20-Nb20^ was published

by Peisman and Holtzberg [7] . However, this diagram does not show the

compound LiNb 0„ which is known to occur in this system [8, 9, 10],

J o nor does it show the solid solution of Nb„0^ in LiNbO_ [11] which ZD J has been found to be important in the production of large optical quality

crystals. A phase equilibrium diagram indicating these corrections v;as previously published [2] ; and this diagram is reproduced here, essentially

unchanged, in figure 1. The experiments performed in this laboratory

to check this diagram are listed in table 1. The unit cell dimensions

of the phases will be given in the summary table of x-ray data near

the end of this report (Table 12)

.

The Nb„0^-LiNbO_ system contains only two intermediate phases, 2d 3 the compound LiKb 0 and another phase which occurs at a very narrow

3 8

compositional range near Li^O : 14Nb20^ . This phase was reported

independently by the present authors [2] and by Norin and Molander [12]

to have the N-Nb„0^ structure. Only this phase and LiNb0_ itself may

2 b 3 be considered to have any interesting non-stoichiometric properties.

A detailed analysis of the work performed in this system, including

x-ray diffraction patterns, will be piiblished in the near future [3].

The System Ta20^-LiTa03

No phase equilibriian diagram for this system had been published prior

to our preliminary work reported in reference [2] . The final phase

diagram, is shown in figure 2 and the experimental data from which it was constructed are listed in table 2. The present diagram differs from that

given in [2] only in the first 5 mole percent Li^O content and near the

melting point of LiTa 0 . Lithium oxide has been found to stabilize the low temperature polymorph of Ta^O^ (L-Ta^O^) ; and, therefore, non-stoichiometric solid solutions

appear on both sides of this system. There is only one intermediate

compound, LiTa 0 , but it is trimorphic and apparently has no appre3 o
ciable non-stoichiometric region within the binary phase diagrant.

The low temperature form of LiTa O is isostructural with LiNb O , the

3 8 JO

intermediate form is isostructural with the mineral wodginite, and

the high temperature form is similar in structure to LiTa^O^^F and

LiNb^O, [13].

6 lb

The unit cell dimensions will be listed in the summary table

of x-ray data near the end of the report (Table 12) and a detailed

analysis of the work performed in this system, including x-ray diffraction patterns, will be published in the near future [3].

The System Nb„0^-NaNbO.

2 b 3

This system has been studied by several different groups and phase equ

libriijm. diagrams were published by Reisman, Holtzberg and Banks [14] , and

by Shafer and Roy [15]. The former group reported a 1:4 and a 1:14 compoxind whereas the second reference shows 1:4, 1:7, and 1:10 compounds.

These type of ratios represent mole ratio of alkali oxide to niobium (or

tantalum) oxide. Sten Andersson [16] has shown that the high Nb.O^ content

Z b

phase occurs at the 1:13 ratio (NaNb^^O^^) from crystal structure analyses

[17] and found the other phase to occur at the 1:3 ratio (NaNb 0 ) . He

3 b

found the compounds Na„Nb.O^, and NaNb^O._(OH) only in hydrotherm.al experi2 4 11 b lb

ments at 500-700°C and 2000 atm. In a crystal structure analysis of

Andersson 's NaNb O crystals, D. C. Craig and N. C. Stephenson decided

3 8

that the composition of the crystal they examined was most likely

The phase equilibrium diagram which we have determined for this system

is given in figure 3 and the experimental data from which it was determined

are listed in table 3. We confirm the 1:13 compound but do not find any

other between this and the "NaNb 0 " phase. The latter is apparently

3 8 a non-stoichiometric solid solution with a tetragonal tungsten bronzetype substructure and an orthorhombic superstructure (TTBs) . In addition

Na^Nb^O^^ v/as found in equilibrium at lew temperatures (below about

1000°C) and specimens near the 1:6 ratio was found to react with atmospheric

moisture at temperatures between about 700-900°C to form NaNb^O^^ (OH) without the necessity for hydrothermal techniques.
The unit cell dimensions of these phases will be listed in the

summary table of x-ray data near the end of the report and a detailed

analysis of the work performed in this system, including x-ray

diffraction patterns, will be published in the near future [4].

The System Ta^O^-NaTaO^

The phase equilibrium diagram for this system had not been reported

prior to our prelim.inary paper [2] although Reisman [19] had made a subsolidus study up to 1300°C. The diagram given in figure 4 is similar

to that of [2] but has been reevaluated for the melting relations of the

distorted tetragonal tungsten bronze-like phase (TTBs) between about

20 and 2 5 mole % Na^O. This is the only non-stoichiometric phase in the

system although apparently a very small amount of Na^O may be incorporated

in L-Ta^O^, increasing the phase transition temperature. The only other

phase in the system, is Na2Ta^0^^ which has a hexagonal structure similar

to the monoclinic Na^Nb^O^^.

The experimental data from, which figure 4 has been constructed are listed in table 4. The unit cell dimensions of these phases will be listed

in the summary table of x-ray data near the end of this report. A

detailed analysis of the work performed in this system, including x-ray

diffraction patterns, will be px±>lished in the near future [4].

The System Nb^O^-KNbO^

2 5 3

A phase equilibrium diagram for this system was previously reported

by Reisman and Holtzberg [20] . Additional information on compound formation,

crystal growth, and unit cell dimensions has been p\iblished by Guerchais

[21], Whiston and Smith [22], and Nassau et_ al_ [23]. The phase equilibrium

diagram determined in the present study is shown in figure 5 and the

experimental data from which it was constructed are listed in table 5.

The system was found to contain six intermediate phases. The unit

cell dimensions of each phase are listed in the sumjnary table near the

end of this report. From these dimensions it is apparent that at least

three of these phases have non-stoichiometric-type structures. These

are designated in the phase diagram as GTB, TTBs, and TTB and occur at

6
about 11.5, 16-20, and 35 mole % K^O respectively. The former has a structure similar to that reported by Gatehouse for a rubidium niobate

phase [24] and herein referred to as a Gatehouse tungsten bronze (GTE)

.

The other two have a c3istorted tetragonal tungsten bronze structure (TTBs)

and an undistorted 'bronze' structure (TTB) respectively.

The unit cell dimensions of the 2:3 phase indicate a layer of niobia

octahedra with all the potash possibly located in planes. The hydrated

form of this phase reveals different x-ray diffraction intensity

distributions depending on the hydration direction and rate. This

phenomena may possibly indicate different distributions of k"^ ions which

depend on the hydration. Ionic conductivity of this phase in a direction

parallel to the cleavage, that is, parallel to the k"*" and/or H^O motion

should be investigated more carefully.

A detailed analysis of the work performed in this system, including

x-ray diffraction patterns, will be published in the near future [5].

The System Ta^O^-KTaO^

The phase equilibrium diagram piablished for the system K-0-Ta„0^

z 2. z> by Reisman e_t al contained only two compounds between Ta^O^ and KTaO^ [25] . The preliminary diagram piiblished by the present authors [2] indicates

nine equilibrium phases in this region and two other metastable phases.

The present diagram, figure 6, differs from the previous only in the

estimated width of the non-stoichiometric phases. The experimental data

from which this diagram was constructed are listed in table 6.

The system was found to contain four stable non-stoichiometric regions

in addition tc five stable, apparently stoichiometric, phases. The phases

with ron-stoichiometric type structures include a Gatehouse tungsten

bronze (GTB) at about 11,5 mole % K^O, an orthorhombic distorted tetragonal

tungsten bronze with superstructure (TTBs) between about 15-20 mole % K^O, a hexagonal tungsten bronze (HTB) at about 21.75 mole % K^O, existing

over a very narrow temperature region below the solidus, and an undistorted tetragonal tungsten broiize with no superstructure at

'"'-34 mole % K^O. Figures 7, 8, 9, and 10 show the results of measuring

the dielectric loss (epsilon) versus temperature at a number of frequencies

7
for these four non-stoi.chiometric phases. The GTE and HTB phases show

excellent ionic mobility. Unfortunately, single crystals of these phases

have not yet been grown. The difficulty is due mainly to the very narrow

primary phase field. An attempt must be made to find a system with wider

primary phase regions for these structures, possibly m systems with 1^2*^'

which can then be ion exchanged.

Other Systems

In the course of this study, a considerable number of specimens

were investigated with compositions not included in the six systems

described previously. The ternary systems involving these six systems

with MoO^ were all examined briefly for the purposes of growth of small

crystals [2] . The compositions of the crystal growth preparations will

be detailed at a later date [3, 4, 5, 6]

.

Several of these six binary systems were also examined in conjunction

with WO^, especially the psuedo-binary joins NaTaO^-WO^ and KTaO^-WO^.

The NaTaO^-WO^ system proved to be completely non-binary and contained

mostly solid solutions of sodium tungstates in the sodium tantalate type

phases. However, the KTaO^-WO^ system is apparently a psuedo-binary system

below the solidus and contains at least five phases. The compositions of

the phases are about 25, 50, 50, 70, and 90 mole % WO^. The ternary system

KTaO^-WO^-K^WO^ has been found to be a promising flux system for crystal

growth of both the pyrochlore and hexagonal tungsten bronze (HTB) type

phases. Further work on this ternary will be conducted in the next year.

Some compositions in the Li„0-Ta_0_-WO_ system were prepared and examined

2 2d 3 for the purpose of introducing non-stoichiometry into the H-LiTa O

3 o structure. Other compositions in the system Li^O-Ta^O^-TiO^ were also

prepared for the same purpose. The WO^ gave single phase non-stoichiometric

solid solutions but showed no ionic mobility (table 7) . The TiO^

specimens did not exhibit solid solution.

A study of the Li O-TiO system or rather of the Li TiO -TiO system

^ 2 2 3 2 revealed only one high temperature intermediate phase. This phase has

the ramsdellite structure; but, unfortunately, melts incongruently with

the peritectic very close in composition and temperature to the eutectic.

8
Thus, single phase crystals could not be pulled from the melt. Experiments in the Li^O-TiO -MoO ternary also did not reveal any ideal

flux compositions for crystal growth of this phase. The ramsdellite

lithium titanate did not exhibit appreciable ionic mobility (table 7)

.

Other experiments with K C-Li„0-TiO„ and K 0-MgO-TiO revealed a new

2 2 2 2 structure type [26] which also failed the ionic mobility screening tests.

The only experiments performed under this contract which did not

involve mixed oxides were conducted in the system. NaF-AlF^-Na^GeF^ in

an attempt to produce Ge doped NaAlF^. These experiments were not

successful and no NaAlF^ was obtained.

4 A few compositions involving the systems NaSbO^-Sb^O^ and KSbO^-Sb^O^

have been prepared in order to survey possible compound formation in

these systems, because Aurivillius [27] has reported k"^ ions to occur in

large tunnels in some potassiimi antimonates. In addition, several

specim.ens were exairined in the ternary systems KSbO^-Sb^O -SiO^ and 2 J. 3 2 4 2 KSbO^-Sb^O^-Al^O^ in an attempt to explain the published data of Spiegelberg

[28] who reported a primitive cubic "polymorph" of KSbO^ prepared in

a porcelain crucible. These experim.ents were successful in demonstrating

+ 4 +3 that a sm.all amount of both Si and Al promote the form.ation of this

cubic polymorph. These and similar antimonate systems will be examined

in greater detail in the coming year.

Polycrystalline Specimen Preparation

The sections of this report dealing with the phase equilibrium

relationships in alkali niobate and tantalate systems have described several

phases which, from structual considerations alone, would appear to be

worthy of screening for their potential as fast ion conductors. Accordingly,

polycrystalline specimens were prepared and submitted to Lewis Research

Center for dielectric and conductivity measurements.

The choice of composition and thermal treatment for use in pellet

fabrication of a desired phase was made on the basis of the compositional

and temperature stability limits of the phase as determined in the phase

equilibrium studies. These limits are not always compatible with the

sintering characteristics of the powders and, as a consequence, it was

9
not possible to prepare high density pellets of some of the phases of

interest. Several alkali titanate pellets of interest were also prepared

as an outgrowth of work under a previous contract. All compositions for use in pellet fabrication were given blending and calcining treatments

similar to those utilized in the preparation of compositions for phase

equilibrium studies. In the case of phases wherein alkali loss was anticipated during sintering or where a minimum temperature of stability

necessitated rapid cooling of the pellets, the exact composition of

the pellet was chosen to give as much latitude as possible in the sintering

treatment. The appropriate 1:1 alkali niobate or tantalate was used as one constituent of the batch in these systems to avoid the use of carbonates.

Conventional ceramic dry pressing and sintering techniques were utilized for pellet preparation. Dry pressing was performed in steel dies

at nominal pressures of the order of 10,000 to 18,000 psi. No organic

binders or other additives were utilized except as noted. In general,

several test heatings were necessary to determine a suitable time-temperature

relationship for sintering. In some cases, excessive recrystallization

during sintering, regardless of the schedule followed, prevented the

formation of physically sound pellets. As discussed below, hot pressing

was found useful in some cases. The starting compositions after calcining, as well as the as-fired

surface and interior of the sintered pellets, were characterized by x-ray

diffraction techniques to insure that the final pellets were homogeneous

and single phase.

Tables 8, 9, and 10 summarize the compositions, heat treatments and

x-ray characterizations of the pellets submitted for evaluation. The

results of screening tests conducted by LeRC are given in Table 7.

Crystal Growth

The growth of large single crystals of the various non-stoichiometric

phases found in the alkali niobate and tantalate systems is comiplicated

by many factors: (1) some of the desired phases do not exist in equilibrium

with the liquid, (2) incongruency , and (3) volatility of the alkali. For

these reasons only a few of the compounds foiurid in the phase equilibrium

10
studies were grown successfully. These were the congruently melting com- pounds and those incongruent compounds which existed in equilibrium, with

a liquid over a wide temperature range. In all crystal growth attempts

the molten material was contained in either platinum or iridium crucibles

which were heated inductively and the desired phase pulled either by the

conventional Czochralski technique, or by an approximation to top seeded

solution growth.

A number of the more interesting phases do not lend themselves to

growth by the more conventional techniques and it will be necessary to

explore various flux growth techniques in an effort to obtain crystals of

a size suitable for physical property measurements.

The crystal growth experiments (table 11) are summarized as follows:

Nb^O^-KNbO^

7:13 Phase (TTB)

Growth of the 7:13 phase was attempted from a melt composition of

36 . 5K 0: 53 . 5Nb„0_ . The first material to crystallize was the 4:9 phase,

2. z b on continued pulling a small amount of 7:3 3 phase crystallized out on the

side of the 4:9 phase as a polycrystalline mass. As the pull continued

the remainder consisted of single phase 2:3. Several different melt

compositions were tried and the results were essentially the same, in

all cases the 4:9 phase crystallizes out and as more material is removed

the composition of the crystallizing phase shifts to the 2:3 phase.

Apparently the temperature-composition region over which the 7:13 exists

in equilibrium is too small to successfully obtain crystals by the

pulling technique.

12X^0 :88Nb20^ (GTB)

Attempts to pull the (GTE) bronze-like phase 12K_0: 88Nb„0^ at a melt

2 2d

composition of 15K„0:85Mb_0^ resulted in a polycrystalline multiphase

2 ZD

mass. This result was not unexpected as an inspection of the phase

diagram indicates a very narrow compositonal range where this phase is

in equilibrium with the melt. This situation makes it extrem.ely difficult

to grow large crystals of the 12:88 phase any place in the K 0-Nb 0^^

11
binary. Only by going to a flux system can one possibly expect to grow

this phase.

17.5K 0:82.5Nb^O^ (TTBs)

2

2 5 Attempts to grow the TTE phase from a melt composition of 20X^0: SONb^O

resulted in essentially single phase polycrystalline TTB with very fine

grain size. This phase would be a likely candidate for top seeded solution

growth (TSSG) or possibly the accelerated crucible rotation technique (ACR)

Ta„0^ :KTaO^

2. b i TTB Phase '

As determined from phase equilibria studies, the TTB phase melts

incongruently . For the crystal growth attempts, a melt composition of

45K 0:55Ta„0^ was chosen. With this composition and using a pull rate of

2. 2d

0.2 in/hr crystals of the desired phase were grown. The maximum diameter

attained was the order of 1/8 in. diameter at the stated pull rate. The

growth of larger crystals would necessitate much slower growth rates, as with top seeded solution growth.

Ta^O^rLiTaO^ System

1:3

Single crystals of the 1:3 phase were grown both "on composition"

and from compositions slightly rich in "^^2^' '^^^ "as-grown" crystals

were light brown to colorless depending upon cooling rate. S\absequent

annealing in air removed all traces of brown color. The reason for this

change in color is not known.

5:95 Phase

The 5:95 phase or L-Ta^O^ has been grown in sizes up to as large as

2 cm long and 1.5 cm diameter. This is an incongruent melting compound

and growth was by top seeded solution growth starting at a composition

of 15Li20 :85Ta20^ . These are the first large crystals of L-Ta^O^ ever

grown and are being used for a structure determination using neutron

diffraction, in order to obtain a better knowledge of the m.echanism of

nonstoichiometry . The crystals are almost colorless when first grown but

gradually turn yellow on exposure to light.

12

' /'
Nb^O^-NaNbO^ System

1:3 Phase

Single crystals of the 1:3 phase could be readily pulled from a melt of the stoichiometric composition, however, there was a problem with

cracking which limited the size of usable crystals obtained. The cause

of cracking was not investigated.

Ta.O^-NaTaO. System

2 5 3 21:79 Phase (TTBs)

All attempts to grow crystals of the bronze- type phase by induction

heating at ambient pressures were unsuccessful due to the rapid loss of

Na20 from the melt.

Structural Mechanisms of Non-stoichiometry in Alkali-Niobates and Tantalates

An abnormally large number of phases have been found in the six systems

examined and discussed in this report. In addition to the end members,

the Li 0 systems contain two and three phases with Nb„0^ and Ta„0^

2 2 5 2 D respectively whereas the Na^O systems contain two and four phases each and

the K^O systems, six and nine phases each. The unit cell dimensions of

each of these phases is listed in table 12 together with the pertinent

crystallographic data where known.

The occurrence of the tungsten-bronze-type structures in these alkali

niobate and tantalate binary systems is somewhat disconcerting, as the

A^BO^ compositional range does not fall in these systems for any

value other than x=l. It is quite evident, therefore, that it is

impossible to have niobixmi and tantaliam oxygen octahedra and pentagonal

bipyramids form in a network structure in which only a non-stoichiometric

amount of alkali ions compensate the freimework for electrical neutrality.

One possible hypothetical alternate of oxygen vacancies is both esthetically

displeasing and structurally unsound. Furthermore, such structures

have not been previously found to exist.

13
HTB

The most likely explanation, and one based on preliminary structural

evidence of a similar phase, is that of interstitial niobium (or

tantalum) ions. B. M. Gatehouse [24] has shown that niobium can occur interstitially in a rubidium hexagonal tungsten bronze structure in the

9-fold tricapped-prism interstitial vacancy common to all of the

tungsten bronze-type structures. Gatehouse has suggested that the

composition of this hexagonal bronze phase would be RbNb^ ^O^ or

22.72 mole % Rt>2^* Some hypotheses can be made, on the basis of Gatehouse's

v/ork, concerning the mechanism of non-stoichiometry in the phases

observed in this study.

In the system Ta^O^-KTaO^; a phase having the hexagonal tungsten

bronze structure has been observed to occur at about 21.75 mole % K^O.

By analogy to the RbNb^ ^O^ phase, this can be considered to be

KTa^ 4^9' However, this formula would indicate 22.72 mole % K^O

which is definitely not the case. The composition 21.75 mole % K^O

would correspond to the formula ^^Ta. .^0. and this non-stoichiometric

0.9b 3 . 41 9

phase must contain alkali vacancies as well as tantalum interstitials.

TTB

This same analogy may be used to explain the non-stoichiometry in

the tetragonal tungsten bronze phases which occur with no sign of

superstructure in both the Ta^O^-KTaO^ and Nb^O^-KNbO^ systems. The

formula for one unit cell of the tetragonal tungsten bronze structure

is A^B^^O^^. If all the B ions have a valence of +5, then the formula

b iU , ^ +1 +5

for the ideal end member would be B^^ 8*^''0 ^''^ 35.71 mole % K^O, In

the Nb^O^-KblbC^ system, this phase has been observed at ^35 mole % K^O

corresponding to the formula K Nb oo^ta- the Ta 0 -KTaO

D . o3 10 . o3 30 2b 3 system, this phase has been observed at "^33 1/3 mole % K^O corresponding

to the formula ^ ^^Ta^^

^ ^^03^

.

I

; 14
GTB

In his paper on riabidiuiT! niobates. Gatehouse discussed a new structure

type containing 4-, 5-, 6-, and 7-sided tunnels which may be partially

occupied by alkali ions. This phase has been called the Gatehouse

tungsten bronze in the present paper and was observed to occur at about

11.5 mole % K„0 in both the Ta-0_-KTaO_ and Nb„0^-KNbO- systems. Gatehouse

2 2 5 3 2 5 3 was unable to arrive at a correct composition for this phase, but in a personal communication confirmed the proposed structure:

"... having recently obtained som.e magnificent lattice image photographs

which completely confirm the basic structure—7-sided holes and all."

The basic formula for this structure is A^E_.0, If all the B ions

8 54 146 ^ have a valence of +5 and the excess is supplied via interstitual B

+ 1 +5 ions then the ideal end member composition would be A„ B_. , _ 8 54 + 2.8 145

This ideal formula would correspond to 12.35 mole % alkali oxide.

The formula for the observed 11.5 mole % composition would be

+5 +5

^-7 /iBc/i J o onOi^^ when B is either Nb or Ta . The solid solution

7.4 b4 + 2.92 146

region probably goes down to at least a composition of K^B^^O^^^^ (10.94

mole % K^O) and possibly even slightly lower in k"^ content. It should

be pointed out that this hypothesis involves k"*" ions in both the six and seven (or possible four) sided tunnels whereas Gatehouse explicitly stated

that the seven- and four-sided tunnels appeared to be empty. It is obvious

that the details of this structure need to be examined with more accurate

data. Dr. Gatehouse has informed us that he is now refining three dimensional

crystal lographic data on his rubidium niobate, and KBS will attempt to do

an accurate single crystal crystallographic study of the chemically well-charac

terized potassium niobate phase.

TTBs

The case of the TTBs phase, that is, the orthorhombic tetragonal

tungsten bronze with superstructure indicating that one of the _a tetragonal

axes is tripled, is more complex then the other three. This phase occurs

in all four systems of sodium and potassium with niobium and tantalum.

In the Nb^O^-NaNbO^ system, it occurs between about 22.5 to 27.5 mole %

Na 0 and between about 19.5 and 25.5 mole % Na O in the Ta O -NaTaO system.

^ 2 2 5 3 15
However, in the Nb^O_-KNbO_ and Ta^O^-KTaO. systems, this same structure

2 5 3 ZD J type occurs between about 15 and 20 mole % K^O. Although the absolute

limits of these have not been accurately located, these rough limits of

about 15 to 27.5 mole % alkali oxide must be explained.

D. C. Craig and N. C. Stephenson [18] have examined the crystal

structure of a specimen of NaNb 0 supplied by S. Andersson [16].

3 o They concluded that the particular crystal examined had the

composition Na. _Nb_^0^. or 27.08 mole % Na 0 rather than the 25 mole %

13 35 94 2 Na^O suggested by Andersson. Stephenson reports that the tripled

"tetragonal-tungsten-bronze" cell has a basic structure of Na Nb 0

b 34 y

4

and that twelve excess positive charges must be accommodated by

Na and/or Nb distributed in the eight 5-sided t\annels. He considers

only the cases of Nb"*"^ + 7Na''' and 2Nb"''^ + 2Na'*' and says that the former

more nearly coincides with the experimental intensities. In this

paper [18] , Craig and Stephenson dismiss the possibility of Nb"^^ in the

three sided tunnels as being "... incompatible with the directional

properties of the bonding orbitals of niobium (V) . " This statement is

subject to considerable doubt and leaves open the actual position of

the "interstitial" niobiiain. Apparently Craig and Stephenson did not

consider the possibility that this phase might have a non-integral

+1 +5 number of Na and Nb ions, that is, be a composition in the middle

of a non-stoichiometric solid solution.

The basic-structure of the tripled tetragonal tungsten bronze (TTBs)

unit cell is, therefore, "'^^34094] ^^'^ contains a maximum of eight

excess positions for alkali ions. The composition can, therefore,

vary from a maximum alkali content of A^^et^ r^0^„ with 28.7 mole %

14 34.8 94

+ 1 +5 alkali oxide to a minimum alkali content of A^ B^^ ^O^ ^ with 14.15

6 36.4 94

mole % alkali oxide. It is noteworthy that the limits of the observed

phases, 15 to 27.5 mole % alkali oxide, occur just within the theoretical

minimum and maximiam values of 14.15 to 28.7 mole % alkali oxide.

In the above four cases, therefore, the most likely structural

mechanism for non-stoichiometry is that of transition metal interstitials

plus alkali ion vacancies. However, other mechanisms can also be found

in the six systems discussed in this report.

16
other Phases

The N-Nb-Or- phase stabilized by Li„0 can be considered to be

2 5 Z ^ Li^0:14Nb„0^ or Li,„(Li^ /,r-Nb_T ^-c)Oor^ with Li ions substituting for

2^ 2 5 lo 0.45 Ji.55 oL) + 5 Nb and also present in interstitial four-sided channels. This

non-stoichiometric phase is thus accounted for by a mechanism of alkali

substitution plus alkali interstitials

.

The high temperature form of LiTa^Og or Li^Ta^O^^ is apparently

isostructural with LiTa^O, and Ta.W^O,^. Either fluorine or tungsten

6 15 4 2 16

ions can be utilized to generate a non-stoichiometric phase and the

structural mechanism is thus alkali ion vacancies plus cation (or anion)

substitution

.

The low temperature form of Ta^O^ (L-Ta^O^) is stabilized by the

2 5 2 5 addition of ^^2^' '^his structure is apparently intrinsically non- stoichiometric with the forTmula Ta^^O^^ and five oxygen "vacancies"

22 55

+ +5

[25] , The Li ions either substitute for Ta creating more anion

vacancies or more likely occur interstitially filling some of the

anion "vacancies" already present or a m.echanism of cation substitution

plus anion interstitials.

It should be rememibered that all of the mechanisms discussed in this

section are hypothetical and must be checked by careful single crystal

x-ray diffraction or even neutron diffraction studies. Until such studies

can be made, our understanding of the structural mechanisms by which

nature compensates a non-stoichiometric phase for electrical neutrality

will remain poorly understood.

17
SUMMARY OF RESULTS

1. The phase equilibria of various alkali tantalates have been studied up to

and including liquidus temperatures and phase equilibrium diagrams have

been constructed most consistent with the experimental data in the systems:

Ta^O^-LiTaO, Zoo

Ta^O^-NaTaO^ ZD J Ta-0^-KTaO_

2. The phase equilibria of various alkali niobates have been studied up

to and including liquidus temperatures and phase equilibrium diagrams

have been constructed most consistent with the experimental data in the

systems

:

Nb^O^-LiNbO^

"

Nb^O^-NaNbO^ 2d 3

. . Nb^O^-KNbO^ /

3. Pellets of nineteen phases were transmitted to the sponsoring agency for

evaluation and the following three compositions were found to show peaks

in the dielectric loss vs. temperature, indicating some ionic mobility.

llK^OrSgTa^O^ - Gatehouse tiongsten bronze structure (GTB)

21.75K20:78.25Ta20^ - Hexagonal tungsten bronze structure (HTB)

34K20:65Ta205 - Tetragonal tungsten bronze structure (TTB)

4. Attempts were made to grow large crystals of eight different phases

and two crystals were transmitted to the sponsor for evaluation.

18
FUTURE WORK

1. The most interesting phases in the K„0-Ta„Op system (GTB and HTB) did

not have phase equilibria relations favorable for crystal growth from

the melt. Preliminary examination of the Rb„0-Nb„0^ and Rb-0-Ta„0^

2 2 b 2 2d

systems suggests that these systems may be more favorable for melt

growth of the GTB and HTB type phases. The phase equilibria in these

systems will be examined in more detail and attempts m.ade to grow

crystals which might then be ion exchanged.

2. Small crystals of the hexagonal tungsten bronze phase in the system

KTaO^-WO^ have been successfully grown from a potassium tungsten

oxide flux. Attempts will be made to grow larger single crystals of

this phase for dielectric loss and/or ionic conductivity measurements.

3. A cubic phase of KSbO^, similar to the high pressure polymorph previously

demonstrated to exhibit ionic mobility, has been successfully synthesized by

the addition of a small amount of either SiO^ or Al^O^. The phase

equilibria of the Sb 0 -NaSbO and Sb 0 -KSbO systems will be studied

and the effects will be studied of various impurities on the stabilization

of the cubic modifications of KSbO^ and NaSbO^ . Attempts will be made to

prepare single crystals of these cubic phases and/or other interesting

alkali antimonates.

19
References

[1] D. R. Kudrak and M. J. Sienko, J. Inorg. Chem. 6_ (1967) 880.

[2] R. S. Roth, H. S. Parker, W. S. Brower and J. L. Waring,

Fast Ion Transport in Solids, Solid State Batteries and Devices,

Ed. W. Von Gool. Proceeding of the NATO sponsored Advanced

Study Institute, Belgirate, Italy, September 1972, North Holland

Publ. Co., Amsterdam (1973) pp. 217-232.

[3] R. S. Roth, H. S. Parker, W. S. Brower (to be submitted to

J. Solid State Chem.)

[4] R. S. Roth, H. S. Parker, W. S. Brower, J. L. Waring and D. B. Minor

to be submitted to J. Solid State Chem.)

[5] R. S. Roth, H. S. Parker, W. S. Brower and J. L. Waring (to be

submitted to J. Solid State Chem.)

[6] R. S. Roth, H. S. Parker, W. S. Brower and D. B. Minor (to be

siabmitted to J. Solid State Chem.)

[7] A. Reisman and F, Holtzberg, J. Am. Chem. Soc. 80 (1958) 6503.

[8] M. Lundberg and S. Andersson, Acta Chem. Scand. 19 (1965) 1376.

[9] M. Lundberg, Acta Chem. Scand. 25_ (1971) 3337.

[10] B. M. Gatehouse and P. Leverett, Cryst. Struct. Comm. 1 (1972) 83.

[11] P. Lerner, C. Legras and J. P. Dumas, J. Cryst. Growth 3, 4 (1968) 231.

[12] R. Norin and B. Nolander, Acta Chem. Scand. _25 (1971) 741

[13] M. Lundberg, Acta Chem. Scand. 19 (1965) 2274.

[14] A. Reisman, F. Holtzberg and E. Banks, J. Am. Chem. Soc. 8£ (1958) 37.

[15] M. W. Shafer and R. Roy, J. Am. Ceram. Soc. £2 (1959) 482

[16] S. Andersson, Acta Chem. Scand 21_ (1967) 1777.

[17] S. Andersson, Acta Chem. Scand. 19 (1965) 557.

[18] D. C. Craig and N. C. Stephenson, J. Solid State Chem. 3 (1971) 89.

[19] A. Reisman, J. Am. Chem. Soc. 66 (1962) 15.

20
[20] A. Reisman and F. Holtzberg, J. Am. Chem. Soc. Tl_ (1955) 2115.

[21] J. E. Guerchais, Bull. Soc. Chim. Fr. (1962) 103.

[22] C. D. Whiston and A. J. Smith, Acta Cryst. 19_ (1965) 169.

[23] K. Nassau, J. W. Shiever and J. L. Bernstein, J. Electrochem. Soc.

116 (1969) 348.

[24] B. M. Gatehouse, D. J. Lloyd and B. K. Miskin, in "Solid State Chemistry"

Proc. 5th Materials Research Symposium, NBS Special Publication

364 (1972) 15.

[25] A. Reisman, F. Holtzberg, M. Berkenblit and M. Berry, J. Am. Chem.

Soc. 78_ (1956) 4514.

[26] R. S. Roth, H. S. Parker and W. S. Brower, Mat. Res. Bull. 8_ (1973) 327.

[27] B. Aurvillius, Arkiv. f. Kemi. 25_ (1964) 505.

[28] P. Spiegelberg, Ark, f. Kemi. Min. och. Geol. 14 [5] (1940) 1.

21
FIGURE CAPTIONS

Phase equilibrium diagram for the system Nb^O^-LiNbO^

redrawn to conform with accepted published data,

o - liquidus [7] e - transition [7] • - solidus and solid solution boundary [7,11]

X - present work

Phase equilibrium diagram of the system Ta^O^-LiTaO^

,

mostly from reference [2]

.

o - completely melted

- - partially melted

• - no melting '

Phase equilibrium diagram of the system Nb^O^-NaNbO^

X - liquidus values from reference [4] o - completely melted

o - partially melted

• - no melting

dotted line - a phase resulting from reaction with atmospheric

moisture

Phase equilibriiam diagram for the system Ta^O^-NaTaO^

o - completely melted

» - partially melted

• - no melting

X - quenched specimen

Phase equilibrium diagram for the system Nb-0_-KNbO.

2 5 3 X - liquidus values from reference [20] o - completely melted

e - partially melted

• - no melting

22
Figure 6 Phase equilibrium diagram for the system Ta^O^-KTaO^

• - solidus and liquidus values from reference [25J o - completely melted

« - partially melted

X - no melting

Figure 7 Dielectric loss (epsilon-2) versus reciprocal temperature

3 -1

(theta =10 X degrees Kelvin ) for a specimen of

llK^OzSgTa^O^ (sample No. 27) having the structure of

the Gatehouse Tungsten Bronze (GTB)

.

Figure 8 Dielectric loss (epsilon-2) versus reciprocal temperature

3 -1

(theta =10 X degrees Kelvin ) for a specimen of

16.67K20:83.33Ta20^ (sample No. 23) having the structure

of a Tetragonal Tungsten Bronze modified by superstructure

to a tripled cell with orthorhombic (TTBs)

.

Figure 9 Dielectric loss (epsilon-2) versus reciprocal temperature

3 —1 (theta =10 X degrees Kelvin ) for a specimen of

21.75K20:78.25Ta205 (sample No. 39) having the structure

of a Hexagonal Tungsten Bronze (HTB)

.

Figure 10 Dielectric loss (epsilon-2) versus reciprocal temperature

3 -1

(theta =10 X degrees Kelvin ) for a specimen of

34K2O: eSTa^O^ (sample No. 28) having the structure

of a Tetragonal Tungsten Bronze with no superstructure

(TTB)

.

23
8001 L_j I 1 I

\ !_J

Nb^O^ 1:14 90 80 70 60 LiNbOj

mol % NbgOg

24
1900

1800

51.4" 1700

I6I0±5

[1600

0 5 10 15 20 25 30 35 40 45 50

Ta205 mol % Li20 LiTaOs

25
1600

1500

1400

1300

1200

ooUJ(TID< MOO

a:

UJ

CL^, 1000

UJ

900

800

700

600

• 4 > •

• • • •

1278°

TTB.

• • • • •

• • • • • •

» r

« %^

, 990",

Nb205 mol % Na20

-•

0 ^ i-u 10 i.JS 20 25 30 ,.35 40 45 50

NaNbOs

26
27
1600

28

)
TQgOg

20 25 30

mo I % KgO
SAMPLE NO. 27

10

10

FREQUENCY • 1.0E 03 SAMPLE NO. 27 FREQUENCY • 1.0E 0*

I

1

0e

i

-%

a 4)V-0

0

II 12 U 16 II 20 22 THETA

10

10 12 THETA

SAMPLE NO. 27 FREQUENCY • 1.0E 05 SAMPLE NO. 27 FREQUENCY • 1.0E 06

10

1

%

0

p(n>w»

OOHj—

0

0•

00

8

9-

0

1 t- 0

10 12 THETA

10 12 14 IC 11 20 2 THETA

Dielectric loss (epsilon-2) versus reciprocal temperature (theta = 10^ x degrees Kelvin"^) for a specimen

OF 11K20:89Ta205 (sample Ho. 27) having the structure of the Gatehouse Tungsten Bronze (GIB).

30
SAMPLE NO. 23

,0 ' FREQUENCY « 1,0E*03

y 10

10

0 ( O"!

2 3

< 5 6 7 8 9 IJ II 12 THETA

SAMPLE NO. 23 FREQUENCY l.OE+04

10

(VI to

i%-

00— —\

8-0 00

0

C

—0

0

2 5 4 5 6 7 THETA

9 10 II 12

SAI'-.'^E NO. 23

10

10

FREQUENCY - 1.0E+05

s

«

0

CD

0

"o

00

0

0c

n

>

i 0

"0

0 —00

9 10 II 12 THETA

SAKRE NO. 25 FREQUENCY - 1.0E+06

10

8

1

i —*

0

n

0

c 0 iCDo" C

—0

0 '^^

)

OOO^g (

) 00 0* a

0

10 II 12 THETA

Dielectric loss (epsilon-2) versus reciprocal temperature (theta = 10^ x degrees Kelvin S for a specimen

OF 16.67K^0:83.33Ta^0^ (sample No. 23) having the structure of a Tetragonal Tungsten Bronze Modified

BY superstructure TO A TRIPLED CELL WITH ORTHORHOMBIC SYMMETRY (TTBs)

31

«
SAMPLE NO. 59 rREQUENCV t.«E*»S SIMPLE NO. 59 TREflUENCY . t,DE*fl4

... .

!

« —

—— ——- — —

0 \0, 0

0 00

40

0

0

0

2 1 9 t J S 9 II II 12

to

10

J 0

QB%

0

0—

.

It0

0

<

0

a'\

00

0

THETA

\ 2 3 < s e 7 e } 10 It 12 THETA

SAMPLE NO. 59 FREQUENCY • t.l)E*05 SAMPLE NO. 59 FREQUENCY • I.OE+OS

%

0

0

8

0 ^oDa —(^—

0 od \

-\

e-tira0

0 0

1

I 2 5 4 S 6 7 THETA

9 10 II

>

oft)*

0

0

0

ft-

( '"°0

(

0 0 — 0

1

0 o" 0

2 3 4 5 S ? THETA

i 10 II 12

Dielectric loss (epsilon-2) versus reciprocal temperature (theta = 10^ x degrees Kelvin'-^) for a specimen

OF 21.75K20:78.25Ta205 (sample No. 30) having the structure of a Hexagonal Tungsten Bronze (HTB),

32

*
SAMPLE NO. 28 fREQUENCY • t.OE+flS

10

<vj 10

.

1 —0

0

0

"o

J-Q

0

00 1 «

0 0 0

1 0 0

0 r

-

'— 0

tt^

-00 0

0

0

0 %

-o-«- 0

-fl

0 0

0

1 2 J < 5 6 7 THETA

9 10 II 12

SAMPLE NO. 28 FREQUENCY - l.OE+04

9 ——

i >%%— — —

00

»- —a 0 row 0 00

3 0(f

-^°o^o '(lOoo^ "o o(b

0-0-

0

I 2 } 4 5 6 7 e 9 10 II 12 THETA

SAMPLE NO. 28 FREQUENCY • 1.0E+05

10

10

»

«

0

%

0Oo

"o

<tr 0

. : 00 o' icoo"^ Oo

0 2345(789 10 II THETA

SAMPLE NO. 28 FREQUENCY - 1.0E+0G

i

CD .o<D004

u %—

u «- ooo—

n 0

0

0

I 2 3 4 S e 7 8 9 10 II 12 THETA

Dielectric loss (epsilon-2) versus reciprocal temperature (theta = 10^ x degrees Kelvin"-^) for a specimen

OF 3')K20;66Ta205 (sample Ho. 28) having the structure of a Tetragonal Tungsten Bronze with no superstructure (TIB)

33
TABLE l! EXPERIMENTAL DATA FOR THE SYSTEM Nb205-LiNb03

Composition Initial Heat

a/ Treatment hi' b/ Temp. Time

°C Hrs. Mole %

Nb205 Li20

97,50 2,50 1000 96

95.00 5,00 1000 63

93,33 6,67 1000 63

92,86 7,14 1000 60

92.31 7,69 1000 63

90.00 10,00 1000 63

33.33 16.67 985 64

80.00 20.00 985 65

75.00 25,00 985 65

70.00 30.00 1000 70,5

66,67 33.33 985 65

63.99 36.01 1000 70,5

Final Heat Treatment c/ Results of Physical Observation

Results of x-Ray Diffraction

Temp, Time

"C Hrs,

—

1202 —20 1249 19 Not melted

1274 24 Not visibly melted

1294 22 Not visibly melted

1318 24 Not visibly melted

1336 23 Some liquid present

1202 20 1249 19 Not melted

1274 24 Not melted

1294 22 Not visibly melted

1318 24 Partially melted

1336 23 Partially melted

-- 1294 —

22

- —

Not melted —

1202 —

20 Not melted

1248 18.75 Partially melted —

1202 —20 Not melted

Not melted

1244 20 Partially melted — — Not melted

1190 96 Not melted

1224 25 Not melted

Not melted

1190 96 Not melted

1224 25 Not melted

1244 20 Partially melted

Not melted

1183 23 Not melted

1195 24 No visible melting

1203 25 Some melting

1207 23 Some melting

1215 24 Some melting

1190 96 Not melted

1224 25 Melted

1183 23 Not melted

1195 24 Partially melted

1203 25 Melted

1207 23 Melted

Analyses d/

H-Nb205 + 1:3 + N-NbjOj (tr)

N-Nb205+ H-Nb205

N-Nb205 + H-Nb205

H-Nb205 + 1:3 N-Nb205

N-Nb205

N-Nb205 ^/

H-Nb205 + 1:3 + N-Nb205

N-Nb205 + H-Nb205 +1:3

N-NboOt- + 1:3

N-Nb,Oc +1:3

1;3 + H-NbjOj

1;3

1:3

N-NboOc + 1:3 + 1:1

1:1 + 1:3

1:1 + 1:3

1:1 + 1:3

~ For ease and accuracy of weighing Li20 was added to Nb205 as LiNb03 not as the oxide

end member.

M./ All specimens were initially calcined in Pt crucibles at the indicated temperature and

time.

c/— All subsequent heat treatments were quenched in sealed Pt tubes from the indicated

temperature.

All phases identified aire given in order of amount present at room temperature

(greatest amount first) . The phases are not necessarily those present at

the temperature to which the specimen was heated. H-Nb205 - the high temperature form of Nb205 N-Nb205 - a metastable form of Nb205 apparently stabilized by Li20. 1:3 - LiNb308

1:1 - LiNb03 solid solution —^ These experiments suggest that the N-Nb205 phase melts incongruently between

1294° and 1318° rather than at the 1268° value given by Reisman,
TABLE 2: EXPERIMENTAL DATA FOR THE SYSTEM TajO^-LiTaO

Initial Heat Final Heat Results of Physical Results of X-Ray Diffraction

Treatment Treatment 2/ observation Analyses —

Temp. Time Temp. Time

"C Hrs. °C Hrs.

1000 60

1600 19.00 No melting H-Ta205 + L-TajOj

1795 0.17 No melting " " 1805 0.17 Partially melted

1600 24.,00 No melting L-Ta205 ss + H-Ta205

1795 0. 17 No melting

1806 0. 25 Partially melted

1000 60

1600 24..00 1795 0..17 1803 0.,17 1842 0. 03 1855 0.,03

1000 60

1794 0.,17 1820 0., 33 1834 0. 33

1000 10 1350 24..00 1594 16.,00 1597 0., 50 1667 0.,17 1732 0.,17 1757 0.,17 1782 0.,17 1809 0. 17

No melting L-Ta205 ss No melting " Partially melted

Partially melted Completely melted

Partially melted

Partially melted

Completely melted

No melting L-Ta205 ss No melting " No melting

No melting

No melting

No melting

Partially melted 'L-la.^O^ ss Completely melted "

1000

1000

1000

10

10

1000 10

1000 10

1550 16,.00 No melting

1550 24..00 No melting

1625 16.. 00 Partially melted

1615 1.,00 Partially melted

1625 0. 75 Partially melted

1627 0.,75 Partially melted

1635 0., 50 Partially melted

1653 0.,50 Partially melted

1663 1. 00 Partially melted

1350 24..00 No melting

1583 0., 50 No melting

1590 16.,00 No melting

1593 0.,50 No melting

1607 0.,75 Partially melted

1618 0.,50 Partially melted

1350 24.,00 No melting

1583 0.,50 No melting

1593 0.,75 No melting

1605 0.,50 Partially melted

L-Ta205 ss

L-Ta205 ss + M-l:3

L-Ta205 ss

L-Ta,0c ss + H-l:3

L-TaoOc ss + H-l:3

L-Ta205 ss + H-l:3 + 1:1

1000 10 1350 24.00 No melting

1580 1.00 No melting

1595 1.00 No melting

1609 0.50 Partially melted

1642 0.50 Partially melted

1646 0.50 Partially melted

1695 0.75 Probably completely melted

H-l:3 + L-Ta205 SS H-l:3 + L-Ta205 ss
75 25 800 1000

30710

1000

1205

1000 1250

10

18

10

30

1130

1143

1144

1077

1111

1126

16.00

16.00 115.00

312.00

307.00 96.00

No melting

No melting

No melting

L-li3 + M-l:3

M-li3

1077 312. 00 No melting » 1110 42.00 No melting n 1111 307. 00 No melting H-ll!3 1126 96. 00 No melting

1130 16.00 No melting I 1143 16.00 No melting M 1144 115.00 No melting M 1205 18.00 No melting

1265 18.00 No melting

1350 24.00 No melting H-ll;3 1573 16.00 No melting

1592 1.00 No melting

1601 1.00 Completely melted

1616 1.50 Completely melted H-li;3 +

H-l:3

H-l:3

70 30 1000 10

66.67 33.33 1000 10

60 40 1000 10

56; 44 1000 10

55 45 1000

,54 46 1000

1350 24

.

, 00 1545 0. 50 1555 0. 50 1566 1. 00 1572 0. 75 1587 0. 50 1594 0. 25

1616 0. 75 1616 0. 50

1350 24

.

,00 1525 2. 50 1551 2. 50 1555 0, 50 1567 1. 00 1578 2. 00

1581 0. 25 1583 3. 00

~~ 1350 24. 00 1547 0. 50 1555 0. 50 1566 0. 50 1572 0. 50 1590 1. 00

1348 66. 00 1440 70. 00 1550 0. 75 1565 0. 50 1576 0. 50 1581 0. 50 1622 0. 50

1348 66. 0 1350 24. 00 1440 70. 00 1550 00

1572 0. 75 1587 0. 50 1606 0. 50 1617 0. 75

1348 66.00

1440 70. 00 1550 1. 00 1581 0. 50 1592 0. 50 1605 0. 50 1612 0. 50 1624 0.50

No melting

No melting

Partially melted

Partially melted

Partially melted

Partially melted

Probably completely melted

No melting

No melting

No melting

Probably some melting

Considerably melted

Completely melted

Completely melted

Completely melted

No melting

No melting

Partly melted

Partly melted

Partly melted

Considerably melted

No melting

No melting

No melting

No melting

No melting

Partially melted

Completely melted

No melting

No melting

No melting

No melting

No melting

Partially melted

Partially melted

Completely melted

No melting

No melting

No melting

No melting

No melting

No melting

Partially melted Completely melted

H-l:3 + 1:1 ss

M-l:3

H-l:3

H-l:3 + 1:1 ss

1:1 ss + H-l:3

1:1 ss 1:1 ss 1:1 ss

+ H-l:3 (tr)

1:1 ss

1:1 ss

36
53 47 1000 10 - 1348

1440

1550

1612

1623

52 48 1000 10 1348

1440

1550

1612

1623

1637

1754

50 50 Starting material

1348

1522

1538

1553

1592

1598

1607

1612

1616

1630

1633

66. 00 No melting 1:;1 70. 00 No melting

1, 00 No melting

0. 50 Just begun to melt

0. 50 Completely melted

~- 1

:

: 1 66. 00 No melting

70. 00 No melting

1. 00 No melting

0. 75 No melting

0. 50 Just begun to melt

0. 33 Completely melted

0. 17 Completely melted

Powder li;1 19. 00 No melting

16. 00 No melting

2. 50 No melting

20. 00 No melting

1. 00 No melting

1. 75 No melting

1. 00 No melting

1. 00 No melting

1. 00 Partially melted

0. 50 Completely melted

1. 00 Completely melted

— For ease and accuracy of weighing, Li20 was added to Ta205 as LiTa03 not as the oxide end member. —^ All specimens were initially calcined in Pt crucibles at the indicated temperatures and time,

c/— Specimens were heated in both open and sealed Pt tubes and seemed to show no difference or discrepancy

in results, as very little, if any, volatilization takes place even from the melt. —^ All phases identified are given in order of cunount present at room temperature (greatest amount first)

.

The phases are not necessarily those present at the temperature to which the specimen was heated.

H-Ta205 - The high temperature polymorph of Ta205.

L-Ta205 ss - A solid solution of the low temperature polymorph of Ta205 stabilized by Li20.

L-l:3 - The low temperature polymorph of LiTa^Og isostructural with LiNb^Og.

M-l:3 - The medium temperature polymorph of LiTa308 isostructural with the mineral woodgenite.

H-l:3 - The high temperature polymorph of LiTa^Og isostructural with LiTagOj^^F and Ta^W20jg.

1:1 ss - A solid solution of LiTa03.

37
TABLE 3: EXPERIMENTAL DATA FOR THE SYSTEM Nb205-NaNb03

Composition

Mole % 1/

Nb205 Na20

95 5

Initial Heat Final Heat

Temp.

°C

750 1000

Time

Hrs.

69

69

Temp.

°C

1200 1250

Time

Hrs.

2121

Results of Physical

Observation

Not malted

Not melted

Not melted

Results of X-Ray Diffraction

Analyses

1:13 + H-Nb205

92.86 7.14 800

1000

1225

69

164

64

875 19.5

900 140

1200 21

1250

1000

67

234

Not

Not

Not

Not

Not

Not

Not

melted

melted

melted

melted

melted

melted

melted

H-Nb205 + li6

1:13

1:13

90.01 9.09 750 1000

69

69 1200 1250

2221

Not melted

Not melted

Not melted

H-Nb205 +1:2

1:13 + TTBs + H-Nb205

1:13 + TTBs

90 10 750 1000

6469 Not melted

H-Nb205 + 1:2 1:13 + TTBs

87.5 12.5 750 1000

69

69

800 114 1225 8

1200

1278

1285

2272

1

Not melted

Not melted

Partially melted

Partially melted

Not melted

H-NbjOs + 1:2 1:13 + TTBs

1:13 + TTBs

83.33 16.67 750 64

1000 69

800

880

900

1200

113

2018.5

22

Not melted

Not melted

Not melted

H-Nb205 + 1:2

1:6 + H-NbjOj + TTBs

TTBs + H-Nb205 + 1:6

1:13 + TTBs Not melted

80 20 750 64

1000 69

800

840

869

880

900

1000

1200

1270

1275 1278

113

70

19

2018.5

67

22

11.5 2.5

Npt melted

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Partially melted

H-Nb205 +1:2

1:6 + H-Nb205 + TTBs

TTBs + 1:6 + H-Nb,Ot

TTBs + 1:13

77 23 870

1100

1100

91

2144 1238 19

TTBs + H-Nb205 + 1:2 TTBs + 1:13 TTBs

75 25 750

1000

1200

900 1000

64

69

21

6296

800 980

1000

1200 1270

1275

1278 1280

800

1225

1225

113

21

11.

2.

1 115

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Completely melted Completely melted

Not melted

Not melted

Not melted

Not melted

H-Nb205 + 1:2

1:6 + TTBs + 1:2 TTBs

TTBs

TTBs
72.92 27.08

70 30

900

900

HOC

750 1000

19 135

44

6469

950

1238

1249

1255

1000

1200

91

19

3, 5 16.5

20

22

Not melted

Not melted

Partially melted

Partially melted

Not melted

Not melted

Not melted

TTBS + li2 + H-Nb20j, TTBs +1:2

TTBs (+ 1:1 ?)

1:2 + 1:1 + H-Nb^Os

1:2 + TTBs (+1:1) e/

TTBs (+1:1 ?) e/

66.67 33.33 800

900

800

1100

800

62

93

62

62

89

950

975

985

985 1000

1073

1200

93

2122

45 169

67

21

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

1:2

TTBs + 1:1

1:2 1:2 (+TTBS + 1:1) trace

1:2 1:2 (+1:1 + TTBs) trace

TTBs + 1:1

65

60

35

40

750

1000

750

1000

64

69

64

69

1:2 + 1:1 + H-Nb,0

1241

1254

1250

1241

1245

1254

1200

1250

19

19

21

19

65

19

2121

Not melted

Partially melted

Not melted

Partially melted

2^5

Not melted

Partially melted

Partially melted

Not melted

Not melted

Partially melted

1:2 + 1:1 TTBs + 1:1 (?)

1:2 + 1:1

1:1 + TTBs

1:2 + 1:1 (+TTBS) 1:1 + TTBs

e/

55

50

45

50

750

1000

750

1000

64

69

6469

1241 19 Not melted

1245 65 Partially melted

1254 19 Partially melted

Not melted

1:1 + 1:2

1:1 + TTBs

Not melted

1:1 + 1:2

1:1

1:1

a/

b/

For ease and accuracy of weighing Na20 was added to Nb205 as NaNb03 not as the oxide end member. — All specimens were initially calcined in Pt crucibles at the indicated temperatures and time.

All subsequent heat treatments were quenched in sealed Pt tubes from the indicated temperature. —^ All phases identified are given in order of amount present at room temperature (greatest amount first)

The phases are not necessarily those present at the temperature to which the specimen was heated.

H-Nb205 - The high temperature form of Nb205

1:13 - NaNbi3033

1:6 - NaNbgOi 5 (OH) . The presence of this phase indicates that the specimen has reacted with

atmospheric moisture.

TTBs - A nonstoichiometric solid solution having an orthorhombic distortion of a tetragonal

tungsten bronze-type lattice with superstructure indicating a tripled unit cell. 1:2 - Na2Nb40ii

1:1 - NaNb03

e/— The presence of a small amount of either 1:1 or TTBs in equilibrium with a large amount of the other

cannot be determined because of a complete overlap of all of the strongest peaks.

39
TABLE 4: EXPERIMENTAL DATA FOR THE SYSTEM TaaOs-NaTaOs

Composition

Mole % -/

Ta205 Na20

95 5

83. 33

80

77.78

16.67

Initial Heat Treatment W

Temp. Time

°C Hrs.

1000 109

1000 109

20 1000 109

1527 16

22.22 800 112

Final Heat

c/ Treatment —

Temp . Time

"C Hrs.

Results of Physical

Observation

Results of X-Ray Diffraction

Analyses

L-TajOg + 1:2 1328 16.00 Not melted

1549 16.00 Not melted H-Ta

1648 0.08 Not melted

1653 0.08 Partially melted

1664 0.08 Partially melted

1679 0.08 Partially melted

1328 15.00 Not melted TTBs

1527 16.00 Not melted TTBs

1625 41.00 Not melted TTBs

1643 0.08 Not melted

1658 0.08 Partially melted

1670 0.08 Partially melted

1195 552.00 No melting

1:2 H

1270 360.00 No melting TTBs

1329 64.00 No melting

1527 16. 00 No melting TTBs

1577 19.00 No melting

1623 17.00 No melting

1643 0. 16 No melting

1654 0.16 Partially melted

1660 0.08 Completely melted

1670 0.08 Completely melted

1195 552.00 No melting TTBs

1270 360.00 No melting

1350 48.00 Not melted TTBs

1527 16.00 Not melted

1642 0.16 Not melted

1654 0.16 Completely melted

2 5

75 25

70 30

1000 109 1:2 + L-Ta205

1195 552. 00 Not melted 1:2 + L-Ta205 + 1270 360. 00 Not melted TTBs + 1:2 1329 54. 00 Not melted

1527 6. 00 Not melted TTBs

1613 17. 00 Not melted

1643 0. 25 Completely melted

1722 0. 08 Completely melted

1527 6 1195 552. 00 Not melted TTBs + 1:2 (tr) 1270 350. 00 Not melted

1722 0.08 1576 15. 00 Not melted TTBs

1000 109

1580 64. 00 Not melted 1:2 + TTBs

1612 0. 08 Not melted

1627 0. 08 Completely melted

66.67 33.33 1000 109 — — Not melted

1329 64.00 Not melted

1524 7.00 Not melted

1601 1.00 Not melted

1620 0.75 Not melted

1633 0.08 Not melted

1655 0.08 Completely melted

1698 0.08 Completely melted

1750 0.08 Completely melted

1805 0.08 Completely melted

1:2

40
60 40 1000 109

1602 5. 00 Not melted

1617 0.08 Not melted

1628 0. 08 Not melted

1632 0. 08 Partly melted

1664 0. 08 Partly melted

1685 0. 08 Partly melted

1690 0. 08 Partly melted

1722 0. 08 Partially melted

1737 0. 08 Completely melted

50 50 600 4 -- -- 1:1 1328 16.,00 Not melted

1527 0., 50 Not melted

1622 0., 50 Not melted

1576 0.,08 Not melted

1782 0.,08 Not melted

1800 0.,08 Not melted

1821 0.,08 Completely melted

— For ease and accuracy of weighing NaaO was added to Ta205 as NaTaOa not as the oxide end member. — All specimens were initially calcined in Pt crucibles at the indicated temperatures and time,

c/— All subsequent heat treatments below about 1650° were quenched in sealed Pt tubes from the indicated

temperatures. Experiment above about 1650° were performed in an inductively heated Ir crucible using

sealed 80/20 Pt/Rh tubes. —^ All phases identified are given in order of amount present at room temperature (greatest amount first) . The

phases are not necessarily those present at the temperature to which the specimen was heated. L-TaaOs - The low temperature polymorph of TaaOs H-Ta205 - The high temperature polymorph of TaaOs

ss - Solid solution

tri - Triclinic

tr - Trace

TTBs - A nonstoichiometric solid solution having an orthorhombic distortion of a tetragonal

tungsten bronze- type lattice with superstructure indicating a tripled cell.

1:2 - Na2Tai+0ll 1:1 - NaTaOi

41
TABLE 5: EXPERIMENTAL DATA FOR THE SYSTEM Nb205-KNb03

Composition

Mo]e % a/

Initial Heat Final Heat Treatment — Treatment

Temp. Time Temp. Time

Mrs. Hrs.

Results of Physical ObservationResults of X-Ray Diffraction

Analyses —

'''

95 750 1000

6969 No melting

1100 114 No melting

1200 69 No melting

1275 20 No melting

1350 20 Partially melted (?)

H-Nb205 +1:3

H-Nb205 + TTBs

H-Nb205 + GTB

90. 54 800 1000

6296

1305 1315

1325

140

46.

17

No melting

No melting

Partially melted

Partially melted

H-Nb205 + TTBs GTB (+H-Nb205 ?) HTB GTB + HTB + ?

10 750 10006969 1100

1200

1250

1275 1290

1350

1360

1375

2369

40

20

16

20

2040

No melting

No melting

No melting

No melting

No melting

No melting

Partially melted

Partially melted

Partially melted

TTBs + H-Nb,0

1:3

2O5

GTB + H-Nb205 (+TTBS ?) GTB + H-Nb205 (trace)

H-NbjOj + GTB + TTBs (?) + HTB (?) H-Nb205 + TTBs + ? H-Nb205 + HTB

5. 5 11.5 800

1000

1515

62

96

18

1200

1300

1515

1190 1200

1200

1210

1230

1325

1335

1350

1300

66

18

1

18

18

66

71

71

17

70. 43

No melting

No melting

No melting

Completely melted

No melting

No melting

No melting

No melting

No melting

Partially melted

Partially melted

Partially melted

Melted

Not melted

TTBs

TTBs GTB

H-Nb205 H-Nb205

GTB GTB

GTB

TTBs

750 1000

69

69 1100

1200

1275 1330

1335 1350

1360

1375

4569

2018

7120

2040

No melting

No melting

No melting

No melting

Partially melted

Partially melted

Partially melted

Partially melted

Partially melted

TTBs + H-Nb205

GTB + TTBs GTB H-NbjOj + HTB + ? GTB + H-Nb205 (?)

H-NbjOj + HTB

975 1250

2391 1275

1310 1332

1335

1355

1515

19

19

18 120

125

1

Not melted

Not melted

Partially melted

Partially melted

Partially melted

Partially melted

Completely melted

(?)

H-Nb205 + TTBs +1:3

TTBs + GTB

GTB + TTBs

TTBs + H-Nb,0c + ?

85 15 975 12502391 1275

1310

1325 1335

1335

1515

19

19

16

19 125

1

Not melted

Not melted

Partially melted

Partially melted

Partially melted

Partially melted

Completely melted

H-NbjOj + TTBs + 1:3 + 2:3 hyd. TTBs + GTB

GTB + TTBs

H-Nb205 + TTBs + ?

84 16 975 125023

91 1275 1310

1335

1515

19

1919

1

Not melted

Not melted

Partially melted

Completely melted

Completely melted

H-NbjOj + TTBs + 1:3 + 2:3 hyd. TTBs + GTB (?)

GTB + TTBs

42
83.66 16.34 750 69 ~ —

1000 69 -- — Not melted

1100 114 Not melted

1176 24 Not malted

1200 69 Not melted

1275 21 Not melted

1279 1 Not melted

1285 1 Partially melted

1287 1 Partially melted

82 18 975 16 — — H-Nb205 + TTBs + 1:3 + 2:3 hyd. 1250 91 — — Not melted

1275 19 Not melted

1335 18 Completely melted ^-

81.25 18.75 800 62 — —

1000 96 — Not melted TTBs

1225 5 Not melted

1275 19 Partially melted (7) 1335 18 Completely melted TTBs + HTB

80 20 750 69 — — 1:3 + H-NbjOj

1000 69 Not melted TTBs + 113"+ 2:3 1100 114 Not melted TTBs

1200 69 Not melted TTBs +1:3

1275 21 Partially melted TTBs

1279 1 Completely melted

900 24 — — TTBs + 1:3 + H-Nb205

1000 59 — — TTBs

775 42 800 65 850 40 (uncalcined) 775 42 TTBs + 1:3 + H-NbjOj

800 65 850 40

1100 45 • TTBs + 1:3 1200 69 Not melted

750 69 — — 1:3 + 2:3 1000 69 — — Not melted 1:3 + TTB

1100 114 Not melted

1200 69 Not melted 1:3

1000 45 Not melted

27 Not melted 1:3 + 4:9

72.2 27.8 800 62 -- -- 1000 96 — — Not melted 1:3 + 4:9

70 30 750 69 -- -- 4:9 + 1:3 1000 69 — — Not melted

1100 114 Not melted .

820 73 1000 79 1100 21 Not melted 4:9 1100 45 Not melted

1188 4 3 Not melted 4:9

1205 2 Not melted

1100 45 Not melted 4:9 + TTB

800 89 -- -- 1:3 + 2:3 1000 164 — -- Not melted TTB + 4:9

975 21 Not melted TTB +4:9

985 45 Not melted TTB + 4:9 1100 114 Not melted

1195 20 Partially melted 4:9

750 64 -- -- 1000 69 — — Not melted TTB

1100 21 Not melted TTB

1195 18 Partially melted TTB

1215 0.17 Melted

1398 1 — -- Melted (?) 1170 2 Not melted TTB

1170 19 Not melted TTB 1183 19 Partially melted TTB + 4:9 + 2:3 hyd. 1189 2 Partially melted

1191 67 Partially melted 4:9 + 2:3 hyd. 800 47 1000 70 — — TTB

1125 8 Not melted TTB

43
63. 5 36. 5 800

1009

62 38 800

1000

60 40 750

1000

55

53. 85

50

45 750

1000

46.15 750

1000

50 750

1000

65

41

65

45

69

69

69

69

69

69

6969

m% milted

il4J m% rogitii

USS 1 mt ffl@ife@i lliS 1. Net melted

1170 2 Partially melted

1180 2 Partially melted

1200 0.5 Melted —

— —

— Not melted

1130 16 Not melted

1143 2 Not melted

1158 1 Not melted

1160 1 Not melted

1165 1 Not melted

1170 2 Completely melted

1180 2 Completely melted

1200 0.5 Completely melted —

— —

— Not melted

1000 20 Not melted

1143 2 Not melted

1158 1 Not melted

1165 1.. Completely laelted 1170 2 Completely melted

1172 2 Completely melted

1180 2 Completely melted —— —

— Not melted —

Not melted

1000 20 Not melted

1100 23 Partially melted

Not melted

(?) TTB

2 : 3 hyd . + TTB

2:3 + TTB

+ 2:3

+ 2:3

+ 1:1

hyd.

1:1 + 1:3 + 2:3

1:1 + 2:3 + 2:3 hyd.

1:1 + 2:3 + 1:3

1:1 + 2:3 + 2:3 hyd.

1:1 + 2:3

1:1 1:1

— For

b/- All

^/ All

^/ All

The

ease and accuracy of weighing was added to Nb205 as KNbOj not as the oxide end member.

specimens were initially calcined in Pt crucibles at the indicated temperatures and time.

subsequent heat treatments were quenched in sealed Pt tubes from the indicated temperatures.

phases identified were given in order of amount present at room temperature (greatest amount first)

phases were not necessarily those present at the temperature to which the specimen was heated.

H-Nb205- - The high temperature form of NbaOs.

1:3 - NaNbsOs.

GTB - Gatehouse Tungsten Bronze - A nonstoichiometric solid solution having a large

tetragonal unit cell with 7-sided tunnels first described by B. M. Gatehouse for

a rubidium niobate of unknown composition.

TTBs - A nonstoichiometric solid solution having an orthorhombic distortion of a tetragonal

tungsten bronze- type lattice with superstructure indicating a tripled cell.

4:9 - A compound having the apparent composition 4K20:9Nb205 (KsNbi 301,9 )

.

TTB - Tetragonal Tungsten Bronze - A nonstoichiometric solid solution having an undistorted

tetragonal lattice with no superstructure.

2:3 - Ki+Nb60l7.

2:3 hyd. - The hydrated form of K^Nb^O-^y in equilibriiim with atmospheric moisture at room

temperature.

1:1 - KNbOs. HTB - A phase resulting from a quenched liquid with an x-ray pattern resembling a hexagonal

tungsten bronze.

? - An unknown phase which apparently results from quenching a liquid.

44
TABLE 6: EXPERIMENTAL DATA FOR THE SYSTEM Ta205-KTa03

Composition

Mole % -/

Ta205 K2O

95 5

Initial Heat Treatment

Temp. Time

"C Hrs.

Final Heat

90

1000

900

109

168

1000 109

1609 17

89 11 800 115

87.5 12.5 900 216

33.33 16.67 800 192 900 168

1000 109

80 20 1000

1617

1618

78.25

77.78

21.75 800

22.22 900

109

16

16

91

168

1581 1602

19

6. 5

c/ Treatment —

'

Temp.

°c Hrs.

1337 16 1549 16 1602 16

1456 168 1500 17 1553 1 . 0 1609 17 1715 1 . 5 1747 1.5 1795 1.5 1521 44 1601 0.75 1619 64 1620 16 1466 168 1500 17 1521 44 1624 0.17

1647 0. 17 1657 0. 17 —

1600 —

12

1601 17 1640 19 —

950

—

360 1100 64

1337 16 1532 16 1610 16 1624 0.17

1634 6.5 1635 0.17

1647 0.17 —

1337 ~

16 1538 16 1614 16 1617 16 1618 16 1325 168 1350 144

1600 6

1549 1.0

1571 1.0 1575 10 1581 19 1602 6.5 1607 0.5 1620 16 1632 19 1549 19 1549 1.0

1571 1.0 1603 0.17 1613 0.17 1624 0.17

Results of Physical

Observation

No melting

No melting

No melting

No melting

No melting

No melting

No melting

Partially melted

Partially melted Partially melted

No melting

No melting

No melting

No melting

No melting

No melting

No melting

No melting

No melting

Partially melted

No melting

No melting

Partially melted

No melting

No melting

Not melted

Partially melted

Partially melted

Partially melted

Not Not Not

Not

Not

Not

Not

melted

melted

melted

melted

melted

melted

melted

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Partly melted (?) Partly melted

Not melted

Not melted

Not melted

Not melted

Not melted

Partly melted

Results of X-Ray Diffraction

Analyses

L-Ta205 L-Ta^O2"5 H-Ta205 + GTB

1:5 + TTBs

TTBs

TTBs + L-Ta205 + H-Ta205

TTBs + H-Ta205 + L-Ta205

GTB + H-Ta205 (?)

HTB + H-Ta,Oc HTB + H-Ta205 + L-Ta205

GTB + H-TaaOs

GTB + H-Ta205 GTB + TTBs

1:5 + L-Ta205

GTB

1:5 + L-Ta,02^5 GTB + TTBs GTB

L-Ta205 + 1:2 1:5

1:5 + TTBs (tr)

TTBs

TTBs

TTBs

GTB + HTB

TTBs + 1:5 TTBs

TTBs + 9L HTB + TTBs

TTBs + 9L + HTB

HTB

HTB

HTB + 9L

HTB + TTBs

HTB + TTBs

45
75 25 900

1000

168

109

73.85 e/

e/

1340

1340

900 1000

1538

1600

26.15 1462

73.67 26.33 1443

e/ 73.5 26.5 1466

72

721.5

109

6468

69

89

64

72.73 27.27 1000 68

1304 96 Not melted

1340 19 Not melted

1579 16 Not melted

1600 68 Not melted

1692 2 Completely melted

1100 64 Not melted

1327 120 Not melted

1340 19 Not melted

1340 72 Not melted

1538 64 Not melted

1575 10 Not melted

1598 0. 5 Not melted

1611 5. 5 Not melted

1634 16 Melted

1646 1. 0 Melted

1600 68 Not melted

1606 16 Not melted

1610 — Not melted

1528 72 Not melted

1603 0. 25 Not melted

1613 0. 25 Melted

1624 0. 25 Melted

Not melted

1304 96 Not melted

1327 120 Not melted

1603 0. 17 Not melted

1613 0. 17 Partially melted

Not melted

1400 48 Not melted

1574 0. 5 Not melted

1574 16 Not melted

1586 16 Not melted

1594 4 Not melted

1603 0. 17 Not melted

1361 24 Not melted

1400 48 Not melted

1573 0. 17 Not melted

1573 16 Not melted

1589 0. 17 Not melted

1629 0. 17 Completely melted

1632 0. 08 Completely melted

1:2 + 1:5 + TTBs TTBs + TTB

9L + HTB

llL + HTB TTBs + TTB TTBs + TTB TTBs + TTB

9L + TTBs

+ 3L

9L + HTB

HTB + H-l:3

9L + HTB

9L + HTB

9L + HTB

9L + TTBs

9L9L

9L TTB TTB

9L + 16L

16L + 9L 16L + 9L

(tr) + IIL

16L

9L + TTB

IIL + 16L

71.43 28.57 1000 68

70

1575

1583

30 1000

103.5

1361 24 Not melted

1438 75 Not melted

1465 336 Not melted

1507 139 Not melted

1578 1 0 Not melted

1583 3 5 Not melted

1591 88 Not melted

1611 0. 08 Not melted

1613 0. 17 Not melted

1618 0. 08 Not melted

1618 16 Not melted

1624 0 08 Melted

1626 1 5 Melted

1694 1 0 Melted

1438 75- 1465 336 1507 137

1361 24 Not melted

1622 1. 0 Melted

TTBs + TTB 9L + TTB

16L + TTB IIL

llL

+ 1:2 + 1:5 + 3L

IIL + TTB

IIL

IIL IIL + TTB

IIL + 16L llL IIL

TTB

IIL

9LTTB (tr)

46
66.67 33.33 800

900

1000

192

168

109

950

1100

798

1340

1340

1515

1538

1616

360

64

163

19

72

64

20

1.0

Not melted

Not melted

Not melted

Not melted

Not melted

Not melted

Partially melted

Completely melted

1:2

1:2

H TTB

1:2

TTB

II TTB IIL

IIL

+ 1:1 + L-Ta205

+ TTB + 3L

+ IIL

+ TTB

+ TTB + 9L

66

65

34

35

800

800

90

112

1400

1350

10

66

Not melted

Not melted

TTB

1:1 TTB (+1:1 ?)

60 40 1000 92

1318 64 Not melted

1368 0.5 Not melted

1412 16 Partially melted

TTB

TTB

+ 1:1

+ 1:1

55 45 1000 92

1318 64 Not melted

1368 0.5 Not melted

1480 18 Completely melted

1:1 + TTB

50 50 600

1340 19 Not melted

1368 0.5 Not melted

1375 0.5 Completely melted

1:1

— For ease and accuracy of weighing K2O was added to Ta205 as Kta03 not as the oxide end member.

V\ / — All specimens were initially calcined in Pt crucibles at the indicated temperature and time,

c/— All subsequent heat treatments were quenched in sealed Pt tubes from the indicated temperatures,

d/~ All phases identified are given in order of amount present at room temperature (greatest amount

first) . The phases are not necessarily those present at the temperature to which the specimen was

heated.

L-Ta205 - The low temperature polymorph of Ta205.

H-Ta205 - The high temperature polymorph of Ta205.

1:5 - KTa50i3 - An orthorhombic compound of undetermined structure.

GTB - Gatehouse Tungsten Bronze - A nonstoichiometric solid solution having a large

tetragonal unit cell with 7-sided tunnels first described by B. M. Gatehouse

for a rubidium niobate of unknown composition.

TTBs - A nonstoichiometric solid solution having an orthorhombic distortion of a tetragonal

tungsten bronze-type lattice with superstructure indicating a tripled cell.

HTB - Hexagonal Tungsten Bronze - A nonstoichiometric solid solution with an x-ray pattern

resembling a hexagonal tungsten bronze.

9-L - A hexagonal phase with a £-axis 9 x 4 A. 16-L - A hexagonal phase with a £-axis '^^ 16 x 4 A. 11-L - A hexagonal (rhombohedral) phase with a £-axis 11 x 4 A. 3-L - An apparently metastable hexagonal phase with a £-axis 3 x 4 A. 1:2 - K2Ta40ii.

H-l;3 - A monoclinic phase which apparently results from quenching a liquid near the

composition K20:3Ta205. TTB - Tetragonal Tungsten Bronze - A nonstoichiometric solid solution having an undistorted

tetragonal lattice with no superstructure.

1:1 - KTa03.

e/ Made from the 1000° calcines of the 75:25 and 72.73:27.27 mixtures.

47
TABLE 7

Summary of LeRC Measurements —^ of Dielectric Loss on Polycrystdlline NBS Samples

Composition Frequency, Hz b/ Resonance

c/

10^ 10-* 10 = 10''

6Li20:17Ti02

•^1.55^^1. 26 (LiTDOj^g

^l.e^go. 8^^3.808

5Li20:95Ta205 —

5Li20:95Ta205

Lil. 8^35. 8^0.2016

54 622

796

401

80

4. 0

64

7

3067

418

194

743.1

59

2

19 18 0.3 0.02

229.8

225

94

711.4

570.7

18

< 0.002

191.9

132

43

700.9

580.3

180.05

No Peaks

No Peaks

AE = 15.1 kcal/mole

P25 = 2.7 X 10^ il-cm

No Peaks

No Peaks

No Peaks

200.9190.4

19

0. 3 190.2

No Peaks

Naio.8Nb34Wi.8095.e

21Na,0: 79Ta^O^

2 2 5 220.3

220.2

210.1210.2

AE > 10 P25 ~ 3 X 10^ fl-cm

No Peaks

Slight Peaks

AE = 5.6 to 6.

255.1

No Peaks

e/

K4NbgOi7-XH20

e/

< 100

< 2

536 854

< 100

< 0.1

264

64

100 < 100 0.1 < 0.1

102

< 1 64< 1

No Peaks, two orientations.

No Peaks, two orientations.

llK^O:89Ta^0c

K9O: 5Ta902U5 e

52

6.1

180.03

43

4.7

180.01

38

2.6

180.01

36

1.1

180.1

High Temp. AE = 10.3 kcal/mo]

'25 = 2 X 10° I2-cm Low Temp. AE = 8 kcal/mole

No Peaks

= 1 X 10° n-cm

e'e" 220.04

220.1

No Peaks

34K20:66Ta205

K0.5iTa0.5iW0.49O3

a/

b/

c/

Measurements made by H. E. Kautz, LeRC.

at 25°C. — Values of AE obtained from £ vs temperature measurements,

d/ hot pressed specimen.

Single crystal specimens, supplied by K. Nassau, BTL.

AE = 7.9 kcal/mole

P25 = 1 X 10'* fl-cm

AE w 20 to 25 kcal/mole

P25 = 6 X 10'^ n-cm

No Peaks.

48
TABLE B

Cowpesitlon

5 Ll20:95 Ta20s

Li20:3 Ta205

(LiTaaOa)

"Substituted LiTasOa'

Lil .8Ta5.8Wo,20l6

"Tetragonal Bronze"

21 Na20:79 Ta205

11 K20:89 Ta205

K20:5 Ta205

K20:4 Ta205

21.75 K20:78.25 Ta205

34 K20:66 Ta205

K.5lTa^5lW_i,903

(Pyrochlore)

AUUVtl TANTALATE PELLET FABRICATION

Calplna Forming

lOOO'C - 144 hours

Slnfrlng

a/

1000°C - 23 hours lOBCC - 44 hours

1000°C - 23 hours

1050°C - 44 hours

1000°C 1050°C

23 hours

44 hours

800°C - 90 hours

800 °C - 90 hours

800'C - 90 hours

800°C - 91 hours

800°C - 90 hours

SOO'C - 34 hours

Hot pressed— 1200°C

Hot pressed— 1300°C

10,000 psi

10,000 psi

10,000 psi

10,000 psi

10,000 psi

10,000 psi

10,000 psi

10,000 psi

10,000 psi

Reflre 1500°C

16.5 hours Refire 700°C

18 hours

1300°C - 22 hours

air quenched

1400°C - 23 hours

air quenched

1400 °C - 17 hours

air quenched

IGOO^C - 12 hours Removed at tem- perature and placed

on chill block for rapid cooling

1500°C - 20 hours

air quenched

1400°C - 20 hours

air quenched

1600 "C - 6 hours Pellet sealed in platinum, welded

closed . Removed

at temperature

and water-quenched

1400°C - 10 hours Cooled at 120°C/hour

950°C - 27 hours Removed at tem- perature and placed in quartz

tube , evacuated

to p ^

10~5 Torr

and sealed to prevent hydration

X^^Rajr

Low Ta205, crystalllnity

improved by refiring

Low Ta205, crystalllnity

improved by refiring

Single phase, LiTaeOisFtype

Single phase, LiTaeOisFtype

Single phase bronze

Single phase

Tetragonal bronze

Tetragonal bronze

After removal of surface layer by

grinding, single

phase hexagonal bronze

Single phase

X-ray of pellet im- pregnated with silicone

resin to prevent

hydration showed single

phase pyrochlore

Hot pressing performed by the Haselden Co., San Jose, California.

49
Composition

Li20:14 Nb205

Na20:13 NbaOs

Calcine

1000°C - 18 hours

1250°C - 68 hours

800»C - 114 hours

TABLE 9

ALKALI NIOBATE PELLET FABRICATION

Forming Sintering

10,000 psi

10,000 psi

1250°C - 12 hours

Cooled at 180»C/Hr.

1225°C - 8 hours Cooled at ISO'C/Hr.

X-Ray

Single phase N-^Q^205 after surface grinding

Single phase except

for one line of phase

next highest in Na20 content

.

NaNb308

Maio.8(NbO)4(WO) l.eNbsoOgo

11.5 K20:88.5 Nb205

3 K20:13 Nb205 f

800°C - 62 hours

1000°C - 96 hours

800 °C - 89 hours

1000°C - 70 hours

800°C - 62 hours

1000°C - 96 hours

800 °C - 62 hours

1000 °C - 96 hours

18,000 psi

18,000 psi

18,000 psi

18,000 psi

1225°C - 1 hour

air quenched

1225°C - 3 hours

air quenched

1300°C - 6.5 hours

air quenched.

Specimens poorly

sintered. Excessive

grain growth under

all conditions.

Hot pressing in progress

.

1225°C - 1 hour

air quenched

Single phase 1 :

3

Single phase, pattern

similar to NaNbsOs

Gatehouse tungsten

bronze

Tetragonal tungsten

bronze with superstructure .

7 K20:13 Nb205 800°C - 47 hours

1000°C - 70 hours

18,000 psi 1225 °C - 1 hour

air quenched

Tetragonal tungsten

bronze without super- structure .

50
TABLE 10

ALKALI TITANATE PELLET FABRICATION

Composition

Ramsdellite

6 Li20:17 Ti02 (Li_9(Li^3Tii _7)0i()

K20:MgO:4 TiOj

[Ki ,6 (Mq.8Ti3.2>08)

Calcine

9 pbw 6Li20:17Ti02 calcined

800°C - 2.5 Hr. lOSCC - 68.5 Hr.

1 pbw raw batch

6 Li2C03:17 TiO;

eOO°C - 18 hours

100O''C - 24 hours

Forming

10,000 psi

10,000 psi 0.5 percent by

weight stearic

acid as binder.

Sintering

1200''C - 17 hours

air quenched.

1200OC - 13 hours

air quenched

X-Bay

Single phase Ramsdellite

Single phase,

"Cmcm-phase"

System

K20-Nb205

K20-Ta205

Li20-Ta205

Na20-Nb205

Na,0-TaoOc;

Phase

7:13 (TTB) 17.5:82.5 (TTBs) 17.5:82.5 (TTBs) 12.5:81.5 (GTB)

1:2 (TTB)

1:3 5:95 (L-Ta205)

1:3 (TTBs)

21:79 (TTBs)

TABLE 11 Summary of Crystal Growth Experiments

Melt Composition Method

36. 5K20:63. 5Nb205 17.5K20:82.5Nb205

20. OK2O: 80. 0Nb2O5

15. 0K2O:85. 0Nb2O5

45K20:55Ta205

25Li20: 75Ta205 15Li20:85Ta205

25Na20:75Nb205

25Na20:75Ta205

TSSG* TSSG TSSG

TSSG

TSSG

Czochralski

TSSG

Czochralslci

Czochrals)(i

Comments

Yield: 4 : 9 -> small amount 7:13 -> 2:3 Yield: polycrystalline multiphase

Yield: polycrystalline TTB

Yield: Nb205

Yield: single phase

Yield: single crystals

Yield: single crystals

Yield: single crystals

Excessive vaporization of Na20

* Top seeded solution growth.

51
TABLE 12 Crystallographic Data for Phases in the Nb205-Alkali Nlobate and Ta205-Alkali Tantalate Systems

Designation Compos ition Symmetry Unit Cell Dimensions Conditions Probable

Mol a b 0 a g Y Limiting Space Group

A I Possible

Reflections

Nb205 Li20 N-Nb205 93. 33 6. 67 Monoclinic 25. 518 3. 827 17 554 124°59. 1' hkt:h+k = 2n C2,Cm,C2/m

1:3 75 25 Monoclinic 7. 457 5. 035 15 264 107°18. 7' h0i;i=2n P2i/c 0k0:k=2n

TajOs Li20 L-Ta205SS 95 5 Orthorhombic 6. 198 40. 29 3 888 None pm.pq

L-1: 3 75 25 Monoclinic 7. 41 5. 10 15 12 107'>12' h01:t=2n P2i/c

OkO : k=2n

M-1: 3 75 25 Monoclinic 9. 420 11. 536 5 055 91°32' hk!:h+k=2n Cc,C2/c

h02 : 4=2n H-l:3 75 25 Orthorhombic 16. 716 8. 941 QV.l:l=2n Prnma, P2 ^ma. Pm2a

Nb205 Na20

1:13 92.86 7. 14 Monoclinic 22. 40 3.834 15. 37 91°28. 2' — hk8,:h+k=2n C2,Qr,,C2/m 1:6** 80 20 Orthorhombic ^.14. 7 ^10.2 9 hk2:h+k=2n C222,Cm2m, Cmm2,Cmmm

TTBs 75 25 Orthorhombic 12. 364 36. 992 3. 955 Okt:k=2n Pbam, Pba2

i

hOi:h=2n

i:2 66. 67 33. 33 Monoclinic 10. 840 6.162 12. 745 106°13. 2' hke:h+k=2n Cc,C2/c

hOZ:4=2n

Ta205 Na20

TTBs 80 20 Orthorhombic 12. 397 37. 34 3. 903 hOe:h=2n Pmam, P2 jam, Pma2 TTBs • 75 25 Orthorhombic 12. 398 37. 28 3. 899 hOI!:h=2n " " 1:2 66.67 33. 33 Hexagonal 6. 120 36. 629 hki:-h+k+i=3n R3c,r3c h0^:e=2n

NbjOj KjO GTB 88. 5 11. 5 Tetragonal 27 518 3 .9687 h00:h=2n P42l2,P42im

TTBs 83. 33 16. 67 Orthorhombic 12 519 37 . 558 3 952 h0i:h=2n Pmam » P 2 1 am

,

Pma2 TTBs 80 20 Orthorhombic 12 54 5 37.636 3 957 HTB Unknown* Hexagonal 7 511 3 889 None P6/mmm

1:3 75 25 Orthorhombic 8 925 21. 232 3 808 hkt:k+l=2n Amam, A2 jam. hOi:h=2n Ama2 4:9 69.23 30. 77 Triclinic 13 353 13.915 15 022 82''H.a 69''42 89°4.3' None P) ,P1 .TTB- -

- ; - 65 35 Tetragonal 12 589 3 981 h0l:h=2n Pmam, P2 jam. Pma2

2: 3 60 40 Orthorhombic 7 822 33. 019 6 481 hOi:h+^=2n Pmnb,P2inb

hkO:k=2n

2:3 hyd. 60 40 Orthorhombic 7 824 38.073 6 485 hOO:h=2n P2,2i2, OkO:k=2n 00t:l=2n

Ta205 KjO GTB 88. 5 11. 5 Tetragonal 27 55 3 899 h00:h=2n P42i2, P42im

1:5 83. 33 16. 67 Orthorhombic 5 654 10. 713 16 80 hO!l:i=2n Pbcm,Pbc2i Okt:k=2n

TTBs'' - - * 80 20 Orthorhombic 12 547 37. 641 3 922 h08,:h=2n Pmam,P2iam,

Pina2 HTB 78. 25 21.75 Hexagonal 7 527 3 901 None P6/mmm

9L 73. 85 26. 15 Hexagonal 7 55 36 583 hh«:e=2n P63mc,P62c, P63mmc 16L 73.5 26. 5 Hexagonal 7 542 65 57 hhl:e=2n

IIL 71.43 28. 57 Hexagonal 7 54 43 512 hke:-h+k+l=3n R3,R3,R32, R3m,R3m

1:2 66.67 33. 33 Hexagonal 6 283 36 878 hkl:-h+k+S=3n TTB 66 34 Tetragonal 12 569 3 957 h0l:h=2n Pmam,P2^am,

Pma2

3L« 75 25 Hexagonal 9 051 12 284 hOt:t=2n P63Cm,P6c2, P63mcm

H-1: 3* 75 25 Monoclinic 14 615 3. 774 6 557 98° 30' None P2,Pm,P2/m

~ Two dimensional plane groups.

* Metastable phase obtained from quenched liquid.

** Probably due to reaction with atmospheric moisture-NaNbgOj^ (OH)

52
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777 14th Street, N.W.

Washington, D.C. 20005

Dr. R. Goodman

Globe-Union, Inc.

P.O. Box 591

Milwaukee, Wisconsin 53201

Dr. J. E. Oxley

Gould Ionics, Inc.

P.O. Box 3140

St. Paul, Minnesota 55165

Grumman Aerospace Corporation

S. J. Gaston, Plant 35, Dept. 567

Bethpage, Long Island, N.Y. 11714

Battery and Power Sources Division

Gulton Industries

212 Durham Avenue

Metuchen, New Jersey 08840

Dr. P. L. Howard

Centreville, Maryland 21617

57
Dr. M. E. Ellion, Manager

Propulsion & Power Systems Lab.

Bldg. 366, MS 524

Hughes Aircraft Co.

El Segundo, California 90245

Mr. R. Hamilton

Institute for Defense Analyses

400 Army-Navy Drive

Arlington, Virginia 22202

Dr. R. Briceland

Institute for Defense Analyses

400 Army-Navy Drive

Arlington, Virginia 22202

Mr. N. A. Matthews

International Nickel Company

1000-16th Street, N.W.

Washington, D.C. 20036

Dr. Richard E. Evans

Applied Physics Laboratory

Johns Hopkins Univ.

8621 Georgia Avenue

Silver Spring, Maryland 20910

Dr . A. Moos

Leesona Moos Laboratories

Lake Success Park, Community Drive

Great Neck, New York 11201

Dr. R. A. Wynveen, Pres.

Life Systems, Inc.

23715 Mercantile Road

Cleveland, Ohio 44122

Dr. James D. Birkett

Arthur D. Little, Inc.

Acorn Park

Cambridge, Massachusetts 02140

Mr. Robert E. Corbett

Dept. 62-25, Bldg. 151

Lockheed Aircraft Corporation

P.O. Box 504

Sunnyvale, California 94088

Mr. S. J. Angelovich

Chief Engineer

Mai lory Battery Company

South Broadway

Tarrytown, New York 10591

Dr. Per Bro

P. R. Mallory & Co., Inc.

Library

Northwest Industrial Park

Burlington, Massachusetts 01801

P. R. Mallory & Co., Inc.

Library

P.O. Box 1115

Indianapolis, Indiana 46206

Messrs. William B. Collins and

M. S. Imamura

Martin-Marietta Corporation

P.O. Box 179

Denver, Colorado 80201

Mr. A.D. Tonelli, MS 17, Bldg. 22

A3-830

McDonnell Douglas Astronautics Co.

5301 Bolsa Avenue

Huntington Beach, California 92647

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Motorola, Inc.

8000 W. Sunrise Blvd.

Ft. Lauderdale, Florida 33313

Rocketdyne Division

North American Rockwell Corp.

Attn : Library

6633 Canoga Avenue

Canoga Park, California 91304

Mr. D. C. Briggs

WDL Division

Philco-Ford Corporation

3939 Fabian Way

Palo Alto, California 94303

58
Power Information Center

University City Science Institute

3401 Market Street, Room 2210

Philadelphia, Pennsylvania 19014

RAI Research Corporation

225 Marcus Blvd.

Hauppauge, L.I., New York 11787

Southwest Research Institute

Attn: Library

P.O. Drawer 28510

San Antonio, Texas 78228

Mr. Joseph M. Sherfey

5261 Nautilus Drive

Cape Coral, Florida 33904

Dr. W. R. Scott (M 2/2154)

TRW Systems, Inc.

One Space Park

Redondo Beach, California 90278

Dr. Herbert P. Silverman (R- 1/2094)

TRW Systems, Inc.

One Space Park

Redondo Beach, Calif. 90278

TRW, Inc.

Attn: Librarian TIM 3417

23555 Euclid Avenue

Cleveland, Ohio 44117

Dr. Jose Giner

Tyco Labs . , Inc

Bear Hill-Hickory Drive

Waltham, Massachusetts 02154

Union Carbide Corp.

Development Lab. Library

P.O. Box 6056

Cleveland, Ohio 44101

Dr. Robert Powers - Consumer Products Div.

Union Carbide Corporation

P.O. Box 6116

Cleveland, Ohio 44101

Dr. C. C. Hein, Contract Admin.

Research and Develpment Center

Westinghouse Electric Corporation

Churchill Borough

Pittsburgh, Pennsylvania 15235

59

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