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Superconductivity of some new hexagonal tungsten bronzes
Solid State Communications Vol. 4, pp.25-26, 1966. Pergainon Press Ltd. Printed in Great Bri
SUPERCONDUCTW1TY OF SOME NEW HEXAGONAL TUNGSTEN BRONZES P.E. Bierstedt, T.A. Bither and F.J. Darnell Central Research Department*, E. I. du Pont de Nemours and Company, Wilmington, Delaware. (Received 5 November 1965 by J. Krumhansl)
The nonstoichiometric tungsten bronzes M,~WO3with hexagonal structure (maximum x = 0.33) have been described by Magnell’ for the alkali metals potassium, rubidium, and cesium. These materials exhibit metallic-type 2 bronzes having conduction,orand, hexagonal tetragonal as recently I symmetry reported show by Sweedler superconductivity etaL of a series of new hexagonal tungsten bronzes containing the alkaline earths, calcium, strontium, or barium. In addition, the hexagonal thallium and Indium bronzes prepared in this laboratory3 are shown to be superconducting.
THE GROUP U-A hexagonal bronzes were pre-
groups P6 3/mcm, P63 cm or P~c2 with h gonal cell dimensions a = 7.32 A, c = 7.4 The measured density was 8.330 g-cm~ a compared to an X-ray density of 8.414. ‘1 symmetry results 4 who arereported in disagreement tetragonalwit in work ing forofaSlenko series of similar TLAWO3 compon based upon thefrX-ray diffraction powder
pared in super-critical water by reaction of 3MW04/6WO3/W (mol ratio) in sealed gold tubes at 600°Cfor 6 hr under an external argon pressure of 3000 atm. Approximately 2 g of total -4 cmsolids i. d. tubes plus 3with ml of a volume water were of —‘8sealed cm3. into The indium bronze was prepared in a similar manner using In 2 03 In place of alkaline earth tungstate, 3. The T1xWO and the thallium bronze was prepared by the conventional melt fusion technique 3 compound was obtained as purple, hexagonalshaped crystals up to 1 mm long, but the products from supercritical water were obtained only as minute blue-black crystals. Unreacted starting materials were removed from the Ca~WO3bronze by extraction with 40% H3P04 at about 80°C, while 10 per cent aqueous oxalic acid solution other products. was used as extractant for the The stoichiometry of these compounds was determined by chemical analysis and the structure through X-ray diffraction. The DebyeScherrer powder data on all compounds indicated single phase materials with the hexagonal bronze type pattern of Rb0~~WO3as reported by Magn4li Single crystal X-ray measurements on Ti0 30W03 indicated the possible space
patterns. Attempts to demonstrate metallic be of these bronzes by four-probe resistivity measurements on compacted polycrystallii specimens were unsuccessful. In the case Tl~,W03, however, measurement on a gi crystal gave at room temperature a resist of 1.2 x 10.’ c1-cm and a,posl~ivetempera coefficient 1. Metallic of resistivity conductioi~’ aof single 4.2 x ci i~ deg of Ba 0~12WO3 (tetragonal I symmetry) has reported by Conroy and Yokokawa~
(-4~~~) ‘!oF
Superconductivity was measured ma~ cally by observing the self-inductance of a containing the specimen. The ac field was about 1 Oe peak to peak at a frequency of: The temperatures were determined by me~ the vapor pressure of liquid helium. The suits of these measurements are given in’
-
~.
*Contribution No. 1151.
The samples were placed in glass ca 25
26
SUPERCONDUCTiVITY OF SOME NEW HEXAGONAL TUNGSTEN BRONZES
Vol. 4, 1
TABLE 1 Properties of Hexagonal Tungsten Bronzes Compound
Hexagonal cell dimensions* a, A c, A
Ca0~2~,WO3
7.397
7. 569
1.4
Sr0.~W03 Ba~,14WO3 ~ WO3
7.414 7. 307 7. 407
7.569 7.426 7. 545
2. 0 ? ?
Ti0.30W03
7.344
7.482
2.00
*
Superconducting critical temperature Range, °K -
3.4
-
4. 0 2.2 2. 8
-
2,14
-
-
From powder data
tubes, 1 mm i. d. and care was taken to keep 3. the volume of sample constant, 4 x 10~ cm Since the amount of sample was standardized -~
and since only powders were used (thus avoiding skin effects), the height of the transition was taken to be a rough measure of the fractional volume of each sample becoming superconducting In the thallium, strontium, and calcium bronzes, 75-100 per cent of the total volume exhibited superconductivity. Since complete transitions were not observed in the indium and barium bronzes at the lowest temperature of measure-
conducting couldthe notvolumes be calculated. Thesup trr merit (1. 25°K), becoming tion in TL,. 30W03 was considerably sharp~ (a width of only 0. 14°K) than those observ the other bronzes. The existence of these transitions may be due to variable stoichio Acknowledgements We wish to thank J. L, Gillson for the resistivity measurements a H. S. Young for helpful discussions conceri the synthesis of these materials. -
References 1. MAGNELI A., Acts. Chem. Scand. 5, 372 (1951); 7, 315 (1953). 2. SWEEDLER A.R.,
RATJB Ch. J., and MATTHIAS B.T.,
Phys. Lett.
15, 108 (1965).
3. B1THER T.A., U.S. Patent 3,112,992 (1963). 4. SIENKO M.J., 5. CONROY L. E.,
J. Am. Chem. Soc. 81, 5556 (1959). and YOKOKAWA T.,
Inorg. Chem. 4,
994 (1965).
Les bronzes tungstènes M,.,,~WO3non-stoechiom~triques~ structure h~xagonale (maximum x = 0. 33) ont ~f~’d~critspar Magn~li’pour les metaux de potassium alcalin, rubidium et c~sium. Ces matériaux d~montrentune conductivite du type metallique, et ainsi que recemment rapport~par Sweedler etal. ~ des bronzes ayant une sym&rie h~xagonaleou t&ragonale I d~montrentune superconductivit~. Nous voudrions dkrire id la sy-nthese et la superconductivit~ d’une s~riede nouveaux bronzes tungst~neshexagonaux contenant les terres alcalines, le calcium. le strontium ou le baryum. De plus. les bronzes hexagonaux thallium et indium pr~par~s clans ce laboratoire” sent demontr~ssuperconductifs.
SUPERCONDUCTW1TY OF SOME NEW HEXAGONAL TUNGSTEN BRONZES P.E. Bierstedt, T.A. Bither and F.J. Darnell Central Research Department*, E. I. du Pont de Nemours and Company, Wilmington, Delaware. (Received 5 November 1965 by J. Krumhansl)
The nonstoichiometric tungsten bronzes M,~WO3with hexagonal structure (maximum x = 0.33) have been described by Magnell’ for the alkali metals potassium, rubidium, and cesium. These materials exhibit metallic-type 2 bronzes having conduction,orand, hexagonal tetragonal as recently I symmetry reported show by Sweedler superconductivity etaL of a series of new hexagonal tungsten bronzes containing the alkaline earths, calcium, strontium, or barium. In addition, the hexagonal thallium and Indium bronzes prepared in this laboratory3 are shown to be superconducting.
THE GROUP U-A hexagonal bronzes were pre-
groups P6 3/mcm, P63 cm or P~c2 with h gonal cell dimensions a = 7.32 A, c = 7.4 The measured density was 8.330 g-cm~ a compared to an X-ray density of 8.414. ‘1 symmetry results 4 who arereported in disagreement tetragonalwit in work ing forofaSlenko series of similar TLAWO3 compon based upon thefrX-ray diffraction powder
pared in super-critical water by reaction of 3MW04/6WO3/W (mol ratio) in sealed gold tubes at 600°Cfor 6 hr under an external argon pressure of 3000 atm. Approximately 2 g of total -4 cmsolids i. d. tubes plus 3with ml of a volume water were of —‘8sealed cm3. into The indium bronze was prepared in a similar manner using In 2 03 In place of alkaline earth tungstate, 3. The T1xWO and the thallium bronze was prepared by the conventional melt fusion technique 3 compound was obtained as purple, hexagonalshaped crystals up to 1 mm long, but the products from supercritical water were obtained only as minute blue-black crystals. Unreacted starting materials were removed from the Ca~WO3bronze by extraction with 40% H3P04 at about 80°C, while 10 per cent aqueous oxalic acid solution other products. was used as extractant for the The stoichiometry of these compounds was determined by chemical analysis and the structure through X-ray diffraction. The DebyeScherrer powder data on all compounds indicated single phase materials with the hexagonal bronze type pattern of Rb0~~WO3as reported by Magn4li Single crystal X-ray measurements on Ti0 30W03 indicated the possible space
patterns. Attempts to demonstrate metallic be of these bronzes by four-probe resistivity measurements on compacted polycrystallii specimens were unsuccessful. In the case Tl~,W03, however, measurement on a gi crystal gave at room temperature a resist of 1.2 x 10.’ c1-cm and a,posl~ivetempera coefficient 1. Metallic of resistivity conductioi~’ aof single 4.2 x ci i~ deg of Ba 0~12WO3 (tetragonal I symmetry) has reported by Conroy and Yokokawa~
(-4~~~) ‘!oF
Superconductivity was measured ma~ cally by observing the self-inductance of a containing the specimen. The ac field was about 1 Oe peak to peak at a frequency of: The temperatures were determined by me~ the vapor pressure of liquid helium. The suits of these measurements are given in’
-
~.
*Contribution No. 1151.
The samples were placed in glass ca 25
26
SUPERCONDUCTiVITY OF SOME NEW HEXAGONAL TUNGSTEN BRONZES
Vol. 4, 1
TABLE 1 Properties of Hexagonal Tungsten Bronzes Compound
Hexagonal cell dimensions* a, A c, A
Ca0~2~,WO3
7.397
7. 569
1.4
Sr0.~W03 Ba~,14WO3 ~ WO3
7.414 7. 307 7. 407
7.569 7.426 7. 545
2. 0 ? ?
Ti0.30W03
7.344
7.482
2.00
*
Superconducting critical temperature Range, °K -
3.4
-
4. 0 2.2 2. 8
-
2,14
-
-
From powder data
tubes, 1 mm i. d. and care was taken to keep 3. the volume of sample constant, 4 x 10~ cm Since the amount of sample was standardized -~
and since only powders were used (thus avoiding skin effects), the height of the transition was taken to be a rough measure of the fractional volume of each sample becoming superconducting In the thallium, strontium, and calcium bronzes, 75-100 per cent of the total volume exhibited superconductivity. Since complete transitions were not observed in the indium and barium bronzes at the lowest temperature of measure-
conducting couldthe notvolumes be calculated. Thesup trr merit (1. 25°K), becoming tion in TL,. 30W03 was considerably sharp~ (a width of only 0. 14°K) than those observ the other bronzes. The existence of these transitions may be due to variable stoichio Acknowledgements We wish to thank J. L, Gillson for the resistivity measurements a H. S. Young for helpful discussions conceri the synthesis of these materials. -
References 1. MAGNELI A., Acts. Chem. Scand. 5, 372 (1951); 7, 315 (1953). 2. SWEEDLER A.R.,
RATJB Ch. J., and MATTHIAS B.T.,
Phys. Lett.
15, 108 (1965).
3. B1THER T.A., U.S. Patent 3,112,992 (1963). 4. SIENKO M.J., 5. CONROY L. E.,
J. Am. Chem. Soc. 81, 5556 (1959). and YOKOKAWA T.,
Inorg. Chem. 4,
994 (1965).
Les bronzes tungstènes M,.,,~WO3non-stoechiom~triques~ structure h~xagonale (maximum x = 0. 33) ont ~f~’d~critspar Magn~li’pour les metaux de potassium alcalin, rubidium et c~sium. Ces matériaux d~montrentune conductivite du type metallique, et ainsi que recemment rapport~par Sweedler etal. ~ des bronzes ayant une sym&rie h~xagonaleou t&ragonale I d~montrentune superconductivit~. Nous voudrions dkrire id la sy-nthese et la superconductivit~ d’une s~riede nouveaux bronzes tungst~neshexagonaux contenant les terres alcalines, le calcium. le strontium ou le baryum. De plus. les bronzes hexagonaux thallium et indium pr~par~s clans ce laboratoire” sent demontr~ssuperconductifs.