Superconductor technology: apparatus – material – process – High temperature – per se – Having tc greater than or equal to 150 k
Patent
1992-06-16
1993-05-25
Lieberman, Paul
Superconductor technology: apparatus, material, process
High temperature , per se
Having tc greater than or equal to 150 k
423604, 505742, C01F 1700, C01G 302, H01L 3900
Patent
active
052140261
ABSTRACT:
The disclosed superconducting oxide material has a crystal structure of either Nd.sub.2 CuO.sub.4 type or oxygen-deficient perovskite type and mainly consists of a composition having a general chemical formula of (R.sub.1-x A.sub.x).sub.m+1 Cu.sub.m O.sub.3m+1-y, R being at least one rare earth element selected from the group consisting of Pr, Nd, Sm, Eu, Gd, Dy, Tb, Ho, Er, Tm, Yb, and Lu, A being Ce or Th, m being an integer of 1, 2, 3, . . . .infin. (m=.infin. standing for (R.sub.1-x A.sub.x)CuO.sub.3-y), 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.m, Cu in the material having an average valence of not larger than +2 for all R, A, m, x, and y.
The disclosed superconducting oxide material may have a general chemical formula of Nd.sub.2-x-z Ce.sub.x Sr.sub.z CuO.sub.4-y, 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, and 0.ltoreq.z.ltoreq.1.
The above superconducting oxide material can be made by mixing powdery starting materials for the composition, sintering the mixture at 1,000.degree. to 1,100.degree. C. in air, and heat treating the sintered mixture at 900.degree. to 1,100.degree. C. in a reducing atmosphere (with an oxygen partial pressure of less than 10.sup.-2 atm.)
REFERENCES:
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Takagi et al, "Electron-Doped Superconductivity in CuO.sub.2 Layered Compounds with Nd.sub.2 CuO.sub.4 -structure", Mat. Res. Soc. Symp. Proc., vol. 156, 1989, pp. 389-395.
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Akimitsu et al, "Superconductivity in the Nd-Sr-Ce-Cu-O System", Jap. Jnl. Appl. Phys., vol. 27, No. 10, Oct. 1988, pp. L1859-L1860.
Tokura et al, "A Superconducting Copper Oxide Compound with Electrons as the Charge Carriers", Nature, vol. 337, Jan. 26, 1989, pp. 345-347.
Akimitsu et al, "Successive Magnetic Phase Transitions in Nd.sub.2 CuO.sub.4 ", Journal of the Physicl Society of Japan, vol. 58, No. 8, Aug. 1989, pp. 2646-2649.
Nucker et al, "Is Nd.sub.2-x Ce.sub.x CuO.sub.4 an Electron-Superconductor?", Z. Phys. B.-Condensed Matter, vol. 75, Jun. 1989, pp. 421-422.
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Takagi Hidenori
Tokura Yoshinori
Uchida Shin-ichi
Boyd John
Lieberman Paul
University of Tokyo
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