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676 Chapter 14: Phase Diagrams

Fig. 14.31.

---~

' i

--r i

.... ~

I z I

'"I

1100 ~

ii A

9 9

9 o4] 0 Ii Q 9 Q Q 9

, I I 1 ~ .

20 60 80 100

9 rlasa./~ ud

CuO

Temperature vs composition plot for the binary system ofT12Ba2Os-CuO (Jondo

et al.,

1993).

g. Hg-Ba-Ca-Cu-O Systems

The mercury-containing high-T c superconductor oxides

HgBa2Can_lCUnO2n+2+6 ,

where n -- 1, 2, 3 .... have fascinated scientists in recent years. Not only does

this family of compounds exhibit the highest T c among the systems known to date

(Antipov

et al.,

1990), but also, under high pressure, these materials show many

unusual properties, including pressure-induced T c enhancements (Chou, 1996). In

general, a parabolic variation of Tr with 6 and with pressure has been observed

over a wide range of superconductivity values (Loureiro, 1997; Akesenov and

Antipov, 1977; Fukuoka

et al.,

1996; Chu

et al.,

1993; Nufiez-Regueiro

et al.,

1993; Gao

et al.,

1994; Takahashi

et al.,

1993; Jover

et al.,

1996; Ihara

et al.,

1993). Pressure-induced T~ enhancement is still under intense investigation.

Because of the experimental difficulties involving the determination of Hg

vapor pressure, and the toxicity of Hg, very little activity has occurred on phase

equilibrium studies. In this system, the 1201, 1212, 1223, and 1234 phases have

been characterized rather extensively. In Fig. 14.36 the maximum value of the T c

as a function of pressure of various Hg-containing compounds 1201, 1212, 1223,

and 1234 up to 15 GPa is shown (Loureiro; 1997). The initial rate of increase of

T c under pressure appears to be similar for these compounds, indicating that up to

the pressure of 15 GPa, there is a strong intrinsic term controlling T c and charge

E. Summary and Future Needs 677

Fig. 14.32.

90r

860,

82@

" I

~- i

- i

740q

'I T w, ' -

! I 9 Neor~ " " 9

| I 9

I [ .'" S'~gle Phase 2212 "..

9

I ~

9 ~ 9

" "

I "" / ""

\1 9 .."

~ .

9 . . 9 ;

Predomlnont,~ 2212 /

. I

~_~ ~! I

0 5

0212

eo~cuzo,

I \ //

\ /

J i

e,,I

"-!

10 15

Mol

Detoctobte

2212

! l !_

-- w -

20 25

Tl,~ .-,..

Temperature vs composition plot showing the solid solution extent of the T1-2212 phase as a

function of temperature (Cook

et al.,

1990).

transfer is not relevant in this region (Chou, 1996). The slopes at the origin for the

shown fits are Hg-1201: 2.02K/GPa, Hg-1212: 2.2K/GPa, Hg-1223:

2.07 K GPa, and Hg-1234: 1.7K/GPa. A substantial study of P vs T c has been

reported for the Hg-1223 phase (Louvero, 1997). Figure 14.37 shows a summary

of results from various groups; the T~ increased under pressure at a rather strong

rate. The highest pressures reached the onset value of 164 K at around 30 GPa.

Summary and Future Needs

Representative systems of the high-T c superconductors have been summarized.

Special attention was given to the BYC and BRC systems, followed by the

BSCCO systems. These systems have currently been studied most extensively

because of their viable industrial applications in the coated-conductor and

wire/tape development areas. A large number of these diagrams, however,

were by no means complete. For example, a complete series of phase diagrams

678

Chapter

14:

Phase Diagrams

Fig. 14.33.

(1.

3 m

TI-Rich Oxides + Cu0

A ,

131:313

I - TI-Free Phoses

2212

"-E'-"----

&&&

1212

03 .....

(b)

......

log Po2 (Po)

9 . 0

I I

~-Rich Oxides 4- CuO

2223+2212

9 I

9 ~z23 (9ox)/~a3

9

Intenjro~

9 .9 I 9

" .1234

"',..

"'',. .

1J-Free PhoNe " .

"..

9 . 9

9 . .#<~

rl .. "

.... i ........

4 5

log P~ (Po)

Partial p(T120)-p(O2) subsolidus phase diagrams of the system T120-BaO-CaO-CuO with

BaO:CaO:CuO ratios of (a) 2:1:2, and (b) 2:2:3. Compounds formed are:

2212 = T12Ba2CaCu2Ox; 1212 = T1Ba2CaCu2Ox; 2223 = TlzBazCazCu2Ox; 1234 =

T1BazCa3Cu4Ox; 1223 = T1Ba2Ca2Cu3Ox (Tokura

et al.,

1989).

(continued)

E. Summary and Future Needs

679

Fig. 14.33.

(continued)

(c)

_~2-

0 3

I I

TI-Rich Oxides + CuO

&VA

~__ -

aa a 2223

9 I '

9 1234

TI-Fr~ Pho~

"..

1223/2223

Inter'growth

9 .

9 . .r

9 .

! + - f.

4 5

log

P~ (Po)

Partial p(T120)-p(O2) subsolidus phase diagrams of the system T120-BaO-CaO-CuO with

BaO:CaO:CuO ratios of (c) 2 : 3:4. Compounds formed are: 2212 =TlzBazCaCuzOx;

1212 = T1BazCaCuzOx; 2223

-- TlzBa2Ca2CuzOx;

1234 = T1BazCa3Cu4Ox; 1223 =

T1Ba2CazCu30 x (Tokura

et al.,

1989)9

of the BRC systems as a function of oxygen partial pressure and their

corresponding liquidus diagrams are not available. Furthermore, for the coated

conductor research, materials compatibility is an important issue9 Therefore,

information on interactions of high-T c superconductor films with substrates and

other buffer layers is essential. It will be important to have phase equilibrium data

that include the high-To phases and the buffer materials9 In the complicated

multicomponent BSCCO system, complete phase equilibria including Ag are

needed in order to understand Ag's influence on processing by using the PIT

technique. In the other multicomponent systems, only very limited information

on the Tl-containing and Hg-containing systems has been reported.

Besides the systems that have been discussed, other systems of interest to

the high-temperature superconductor research community are Ni-R-C-B, Pb-

Sr-R-Cu-O, Sr-R-Nb-Cu-O, Sr-R-Ga-Cu-O, and the (T1, Pb)Sr-Ca-Cu-O

variants (Cavam 1995). Although these systems are not of immediate industrial

interest, knowledge of the phase relationships of a collection of systems will

contribute substantially to further understanding of the crystal chemistry and

phase equilibria of the high-temperature superconductor oxide family as a whole.

Fig. 14.34.

CeO 2

680

Chapter 14: Phase Diagrams

0 20 Nd2CuO 4 4-0 60 80 100

1/2(Nd203) Mol % CuO

Phase diagram of the (Nd, Ce)CuO 4 system at 1000~ (Kim and Gaskell, 1993).

Fig. 14.35.

8.0

7.0

8.0

9.0

10.0

11.0

-8

1 I i I 1 | -~1~00

N(hOj

Uquld off l

1 `~

o o

1100

Nd203 + N ~ /

:~ ,~'1

Ao ~ .".. or / qlO00

- /

~-:-:/- I,

9 9 9 . ./ .9 . '

9 . . 9 .~ 9 .

- / ..::.~"..~:.-".o./:.. .."J,~

9 .. .. . .'/ 9 .

.- .. .. .~ .'/ . ..

9

O. .9 9 "

.." 9 .." ." 9 .'9

9 ." o" o

.'//."

" -800

0.035

.'" .."

. " . /o'"

.9 ., a 9 0./. 9

0.03

" /"

.. . .9 (@"

- 9 9 .. /.' ."

0.025 9 9 .- 4./"

o .

- 700

9 9 t o " NdljBCe.lsCU04.4

- 9 9 f

9

o.o, O.Ol(" ~176 -

~176 I 9 i I i

-7 -6 -5 -4 -3 -2 -1

k~ Poe UPo

Temperature vs pressure plot showing the effect of oxygen partial pressure on the stability field

of (Nd, Ce)CuO 4. The dotted lines are isocomposition lines (Antipov

et al.,

1993).

E. Summary and Future Needs 681

Fig. 14.36.

180

v 150

[ s o Nunez eL ol. (mix.)

~~/~~'v 0 Takohalhi et oh

140

,L Jover et al,

7/ " Ihoro et ol. (mix.)

.... , ....

10 20 30 40 50

l~mum, GPa

Pressure dependence of T c for the first four members of the mercury cuprates in the HgO-

BaO-CaO-CuO system (Loureiro, 1997).

Fig. 14.37.

llll--I ! 1 1 I I i'l'l ! l i !"'1 ] I I i i

9 9

$ *

9 D

140

i ~ Hg-1201

100

~ Hg-1212

~2o

-'-- H+-~22~

Hg-1234

811 i ! ! i [ I i ! I [ I t I I I I ~ i i

0 5 lo 15

P~mure,

GPa

The superconducting transition temperature T c of Hg-1223 vs pressure P in the HgO-BaO-

CaO-CuO system (Loureiro, 1997; Akesenov and Antipov, 1977; Fuikuoka

et al.,

1996; Chu

et al.,

1993; Nufiez-Regueiro

et al.,

1993; Gao

et al.,

1994; Takahashi

et al.,

1993; Jover

et al.,

1996; Ihara

et al.,

1993).

682 Chapter 14: Phase Diagrams

References

V. L. Akesenov and E. V. Antipov, Phys. Rev. B 55, 3966 (1977).

T. D. Aksenova, P. V. Bratukhin, S. V. Shavkin, V. L. Melnikov, E. V. Antipova, N. E. Khlebova, and

A. K. Shikov, Physica C 205, 271 (1993).

E. V. Antipov, S. M. Loureiro, C. Chaillout, J. J. Capponi, P. Bordet, J. L. Tholence, S. N. Putlin, and

M. Marezio, Physica C 215, 1 (1993).

T. Aselege and K. Keefer, 7. Mater. Res. 3, 1279 (1988).

T. L. Aselege, E. L. Venturini, and S. B. Van Deusen, J Appl. Phys. 75 1023 (1994).

U. Balachandran, A. N. Iyer, P. Haldar, J. G. Hoden, Jr., and L. R. Motowidlo, in K. Kristen and

C. Burnham, eds, Proceedings 4th World Congress on Superconductivity, Orlando, FL, June 27-July

1, 1994. Vol. 2, pp. 639-649.

J. G. Bednorz and K. A. Miiller, Z. Phys. B 64, pp. 189-193 (1986).

R. J. Birgeneau and G. Shirane, in Neutron Scattering Studies of Structural and Magnetic Excitations in

Lamellar Copper Oxides--A Review, Prog. High Temp. Superconduct. (D. M. Ginsberg, Ed.), pp.

151-211.

World Scientific Publishing, Singapore, 1989.

R. Bormann and J. Noelting, AppL Phys. Lett. 54, 2148 (1989).

R. J. Cava, Amer. Ceram. Soc. Bull. 74, 85 (1995).

C. W. Chu, in Proceedings of Quantum Theory of Real Materials, Festschrift to Honor Marvin Cohen,

(J. R. Chelikowsky and S. G. Louie, Eds.), p. 411. Kluwer Academic, Norwell, MA, 1996.

C. W. Chu, L. Gao, E Chen, Z. J. Huang, R. L. Meng, and Y. Y. Xue, Nature 365, 323 (1993).

L. P. Cook, W. Wong-Ng, C. K. Chiang, and L. H. Bennett, in Superconductivity and Ceramic

Superconductors, (K. M. Nair and E. A. Geiss, Eds.), Ceramics Trans. 13. American Ceramics

Society, Westerville, OH, 1990.

D. M. DeLeeuw, C. A. H. A. Mutsaers, C. Langereis, H. C. A. Smoorenburg, and P. J. Rommers,

Physica C 152, 39 (1988).

J. L. Driscoll, J. C. Bravman, and R. B. Beyers, in Appl. Supercond. 1st, Goettingen, Germany, October

4-9, 1992, Vol. 1 (H. C. Freyhardt, Ed.), p. 325. DGM Informationsges., Oberursel, Germany, 1993.

C. E. Fiori, C. R. Swyt, and R. L. Myklebust, "DTSA-NIST/NIH Desktop Spectrum Analyzer Program

and X-ray Database," NIST Standard Reference Database No. 36 (1991).

A. Fukuoka, A. Tokiwa-Yamamoto, M. Itoh, R. Usami, S. Adachi, H. Yamauchi, and K. Tanabe,

Physica C 265, 13 (1996).

Y. Gao, K. L. Merkle, C. Zhang, U. Balachandran, and R. B. Poeppel, 7. Mater. Res. 5, 1363 (1990).

L. Gao, Y. Y. Xue, E Chen, Q. Xiong, R. L. Meng, D. Ramirez, C. W. Chu, J. H. Eggert, and H. K. Mao,

Phy. Rev. B. 50, 4260 (1994).

S. J. Golden, T. E. Bloomer, F. E Lange, A. M. Segadaes, K. J. Vaidya, and A. K. Cheetham, 7. Am.

Ceram. Soc. 74, 123 (1991).

E. Goodilin, M. Kambara, T. Umeda, and Y. Shiohara, Physica C 289, 251 (1997).

A. Goyal, D. P. Norton, J. Budai, E. D. Paranthaman, D. M. Specht, D. M. Kroeger, D. K. Christen,

Q. He, B. Saffian, E A. List, D. F. Lee, P. M. MaNn, C. E. Klabunde, E. Hatfield, and V K. Sikka,

Appl. Phys. Lett. 69, 1795 (1996).

J. Hahn, T. O. Mason, S.-J. Hwu, and K. R. Poeppelmeier, Chemtronics 2, 126 (1987).

E J. Heinrich and D. E. Newbury, Eds., Electron Probe Quantitation, Plenum, New York, 1991.

B. Hettich, B. Freilinger, P. Majewski, T. Popp, and K. Schulze, in High Temp. Superconduct. Proc.

ICMC '90 Conference, Mater. Aspects High-Temp. Supercond., Garmisch-Partenkirchen, Germany,

1990, Vol. 1, (H. C. Freyhardt, R. Fluckiger, and M. Peuckert, Eds.), p. 399. DGM Informationsges.,

Oberursel, Germany, 1991.

T. G. Holesinger, D. J. Miller, and L. S. Chumbley, Physica C 217, 85 (1993).

B. Hong and T. O. Mason, 7. Am. Ceram. Soc. 74, 1045 (1991).

Q. Y. Hu, H. K. Liu, and S. X. Dou, Physica C 250, 7 (1995).

C. R. Hubbard, "Standard Reference Material 675, Fluorophlogopite Powder X-ray Diffraction

Standard" (1982). To obtain, see procedure below for Hubbard et al., (1987).

References 683

C. R. Hubbard, C. Robbins, and W. Wong-Ng, "Standard Reference Material 640b, Silicon Powder X-

ray Diffraction Standard" (1987). Obtainable from the NIST, Office of Standard Reference Materials,

Gaithersburg, MD 20899. Current price will be quoted on request.

ICSD, The Inorganic Crystal Structure Database, Structural Data on Inorganic Phases. Fachinforma-

tionszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen, Germany.

H. Ihara, M. Hirabayashi, H. Tanini, K. Tokiwa, H. Ozawa, Y. Akahama, and H. Kawamura, Jpn. J.

Appl. Phys. 32, L1732 (1993).

J. Jiang and J. S. Abell, in High Temperature Superconductor." Synthesis, Processing and Large Scale

Applications (U. Balachandran, P. J. McGinn and J. S. Abell, Eds.), p. 13. The Minerals, Metals &

Materials Society, 1996.

T. K. Jondo, C. Opagiste, J. L. Jorda, M. T. Cohen-Adad, E Sibieude, M. Couach, and A. E Khoder,

J. Alloys Compd., 195(1-2), (1993).

J. D. Jorgenson, M. A. Beno, D. G. Hinks, L. Soderholm, K. J. Volin, R. L. Hitterman, J. D. Grace, I. K.

Schuller, C. U. Segre, K. Zhang, and N. S. Kleefische, Phys. Rev. B 36, 3608 (1987).

D. T. Jover, R. J. Wijngarrden, H. Wilhelm, R. Griessen, S. M. Loureiro, J.-J. Capponi, A. Schilling, and

H. R. Ott, Phys. Rev. B. 54, 4265 (1996).

S. Kaesche, P. Majewski, and F. Aldinger, J Electron. Mater. 24(12) 1829 (1995).

P. Karen and A. Kjekshus, J Solid State Chem. 94, 298 (1991).

P. Karen, A. Kjekshus, Q. Huang, V. Karen, A. D. Mighell and A. Santoro, submitted to Physica C

(1999).

J. S. Kim and D. R. Gaskell, Physica C 209, 381 (1993).

D. Klibanow, K. Sujata, and T. O. Mason, J Am. Ceram. Soc. 71, C-267 (1988).

K. Knizek, E. Pollert, D. Sedmidubsky, J. Hejtmanek, and J. Pracharova, Physica C 216, 211 (1993).

G. Krabbes, W. Bieger, U. Wiesner, M. Ritschel, and A. Teresiak, J Solid State Chem. 103, 420 (1993).

G. Krabbes, W. Bieger, and U. Wiesner, Trans. Mater. Res. Soc. Jpn. 19A, 463 (1994).

Y. Le Page, T. Siegrist, S. A. Sunshine, L. T. Schneemeyer, D. W. Murphy, S. M. Zahurah, J. V.

Waszczak, W. R. McKinnon, J. M. Tatscon, G. W. Hull, and L. H. Green, Phys. Rev. B 36, 3617

(1987).

E. M. Levin, C. R. Robbins, and H. E McMurdie, Phase Diagrams for Ceramists, Vol. I. American

Ceramic Society, 1964.

T. B. Lindermer and A. L. SuRer, Jr., Oak Ridge Natl. Lab. Report ORNL/TM-10827 (1988).

S. M. Loureiro, "The Synthesis and Structures of Superconductors of Mercury", Ph.D. thesis, CNRS,

Grenobles, France, 1997.

J. I.

MacManus-Driscoll and J. C. Bravman, J. Am. Ceram. Soc. 77, 2305 (1994).

R Majewski, Adv. Mater. 4, 508 (1992); Adv. Mater. 6, 460 (1994).

P. Majewski, in High Temperature Superconducting Compounds: Processing and Related Properties,

(S. H. Whang and A. DasGupta, Eds.), p. 61. The Minerals, Metals & Materials Society, 1996.

P. Majewski, B. Hettich, H. Jaeger, and K. Schulze, Adv. Mater. 3(1) 67 (1991).

E Majewski, B. Hettich, N. Ruffer, and E Aldinger, J. Electronic Mater. 22, 1259 (1993).

R Majewski, S. Elschner, and E Aldinger, Physica C 249, 234 (1995a).

R Majewski, S. Elschner, and E Aldinger, Physica C 249 [34] 234-240 (1995).

A. P. Malozemoff, W. Carter, S. Fleshier, L. Fritzeneier, O. Li, L. Masui, R Miles, D. Parker, R. Parrella,

E. Podtburg, G. N. Riley, Jr., M. Rupich, J. Scudiere, and W. Zang, Proc. Applied Superconductivity

Conf., Palm Desert, CA, Sept., 13-18, 1988; in press.

R. W. McCallum, K. W. Dennis, L. Margulies, and K. J. Kramer, in Processing of Long Lengths

Superocnd. Proc. Symp., Pittsburgh, Pennsylvania, October 17-21, 1993. (U. Balachandran, E. W.

Collings and A. Goyal, Eds.), p. 195. Minerals, Metals & Materials Society, Warrendale, PA, 1994.

N. Merchant, J. S. Luo, V. A. Maroni, G. N. Riley, and W. L. Carter, Appl. Phys. Lett. 65(8), 1039

(1994).

C. Michel, M. Hervieu, M. M. Borel, A. Grandin, E Deslandes, J. Provot, and B. Raveau, Z. Phys. B 68,

421 (1987).

D. E. Morris, A. G. Markelz, B. Fayn, and J. H. Nickel, Physica C 168, 153 (1990).

684

Chapter

14:

Phase Diagrams

R. Muller, T. Schweizer, P. Bohac, R. O. Suzuki, and L. J. Gauckler, Physica C 203, 299 (1992).

National Institute of Standards and Technology, NIST Crystal Data (a database with chemical and

crystallographic information compiled and evaluated by the NIST Crystallographic Data Center).

National Institute of Standards and Technology, Gaithersburg, MD 20899.

National Institute of Standards and Technology, NIST/Sandia/ICDD Electron Diffraction Database,

NIST Crystallographic Data Center. National Institute of Standards and Technology, Gaithersburg,

MD 20899.

National Institute of Standards and Technology, Phase Diagrams for Ceramists, CD-ROM version.

American Ceramic society, Westerville, OH 43081-8720.

M. Nevefiva, E. Pollert, and P. Honskus, Physica C 199, 328 (1992).

M. Nufiez-Reguiero, J.-L. Tholence, E. V. Antipov, J.-J. Capponi, and M. Marezio, Science 262, 97

(1993).

M. Paranthaman, A. Goyal, E A. List, E. D. Specht, D. E Lee, P. M. Martin, Q. He, D. K. Christen, D. P.

Norton, J. D. Budai, and D. M. Kroeger, Physica C 275, 266 (1997).

Phase Diagrams for Ceramists. American Ceramic Society, Westerville, OH 43081-8720.

C. N. Pieczulewski, K. S. Kirkpatrick, and T. O. Mason, J. Am. Ceram. Soc. 73(7) 2141 (1990).

J. Ritter, Powder D/ft. 3, 30 (1988).

R. S. Roth, Proc. User Aspects of Phase Equilibria, Joint Research Centre, Petten, The Netherlands,

June 25-27, 1990. Institute of Metals, London, 1990.

R. S. Roth, C. J. Rawn, E Beech, J. D. Whitler, and J. O. Anderson, in Ceramic Superconductors II

(M. E Yan, Ed.), Publ. American Ceramic Society. 13 1988.

R. S. Roth, C. J. Rawn, B. P. Burton, and E Beech, J. Res. Natl. Inst. Stand. Technol. (USA) 95, 291

(1990).

K. H. Sandhage, G. N. Riley, Jr., and W. Carter, J. Metals 43, 21 (1991).

K. Sato, T. Hikata, H. Mukai, M. Ueyama, N. Shibata, T. Kato, T. Masuda, M. Nagata, K. Iwata, and

T. Mitsui, IEEE Trans Mag. 27 1231 (1991).

M. P. Siegal, E. L. Venturini, B. Moroin, and T. L. Aselege, J. Mater. Res. 12(11), 2825 (1997).

E. D. Specht, C. J. Sparks, A. G. Dhere, J. Brynestad, O. B. Cavin, D. M. Kroeger, and H. A. Oye, Phys.

Rev. B: Condens. Matt, 37, 7426 (1989).

Y. S. Sung and E. E. Hellstrom, Physica C 255, 266 (1995).

H. Takahashi, A. Tokiwa-Yamamoto, N. M6ri, S. Adachi, H. Yamauchi, and S. Tanaka, Physica C 218,

1 (1993).

T. H. Tiefel, S. Nakahara, J. E. Graebner, H. M. O'Bryan, R. A. Fastnacht, and G. W. Kammlott, Appl.

Phys. Lett. 56, 1287 (1990).

Y. Tokura, H. Takag, and S. Uchida, Nature 337(26), 345 (1989).

Toth Information Systems, CRYSMET--Structural Data on Intermetallic Phases. Developed and

maintained by Toth Information Systems, Inc., Ottawa, Canada, K1J 6B2.

J. E. Ullman, R. W. McCallum, and J. D. Veroeven, J. Mater. Res. 4, 752 (1989).

T. A. Vanderah, R. S. Roth, and H. E McMurdie, Phase Diagrams for High T c Superconductors II,

American Ceramic Society, 1991.

J. D. Whitler and R. S. Roth, Phase Diagrams for High T c Superconductors I. The American Ceramic

Society, 1991.

W. Wong-Ng, "XRD Industrial Application to High T c superconductors", in Industrial Applications of

X-ray Diffraction, (D. K. Smith and E Chung, Eds.). Marcel Dekker, New York, 1999, in press.

W. Wong-Ng and L. P. Cook, J. Amer. Ceram. Soc. 77, 1883 (1995).

W. Wong-Ng and L. P. Cook, J. Natl. Inst. Stand Tech. Res. 103, 379 (1998).

W. Wong-Ng, L. P. Cook, C. K. Chiang, L. Swartzendruber, L. H. Bennett and J. E. Blendell, and D.

Minor, J. Mater Res. Sot., 3, 832 (1988).

W. Wong-Ng, B. Paretzkin, and E. R. Fuller, Jr., J. Solid State Chem., 84, 117 (1990)

W. Wong-Ng, R. L. Snyder, C. Park, E. Antipov, and W. E McClune, Powd Diff. 12, 13 (1996).

W. Wong-Ng, L. P. Cook, E Jiang, W. Greenwood, U. Balachrandran, and M. Lanagan, J. Mater Res.

12(11), 2855-2865 (1997).

References 685

W. Wong-Ng, L. P. Cook, and J. Feng,

J. Amer. Ceram. Soc.,

81, 1829 (1998).

X. D. Wu, S. R. Foltyn, P. N. Arendt, W. R. Blumenthal, I. H. Campbell, J. D. Cotton, J. Y. Coulter, W. L.

Hults, M. P. Maley, H. E Safar, and J. L. Smith,

AppL Phys. Lett.

67, 237 (1995).

R. G. W. Wyckoff,

Crystal Structures Series.

John Wiley & Sons, New York, London, Sydney.

S. I. Yoo and R. W. McCallum,

Physica C

210, 147 (1993).

W. Zhang and E. E. Hellstrom,

Physica C

218, 141 (1993).

W. Zhang and K. Osamura, pp. 437-440 in

Adv. Supercond. IlL Proc. 3rd Int. Symp. Supercond.

International Superconductivity Technology Center, Sendai, Japan, November 6-9, 1990 (K.

Kajimura and H. Hayakawa, Eds.). Springer-Verlag, Tokyo, 1991.

R. Zhou, W. L. Hults, J. E Bingert, J. Y. Coulter, E. J. Peterson, and J. L. Smith,

Physica C

249, 166

(1995).