Superconductor technology: apparatus – material – process – High temperature – per se – Having tc greater than or equal to 150 k
Patent
1991-10-15
1993-09-14
Lewis, Michael
Superconductor technology: apparatus, material, process
High temperature , per se
Having tc greater than or equal to 150 k
505725, 505780, H01L 3912
Patent
active
052448681
ABSTRACT:
The disclosed method can produce high T.sub.c superconductor material e.g., YBa.sub.2 Cu.sub.3 O.sub.7) of substantially increased intra-grain critical current density (J'.sub.c), as compared to conventionally produced bulk material of analogous composition. Exemplarily, YBa.sub.2 Cu.sub.3 O.sub.7 pellets produced according to the invention had J'.sub.c of about 10.sup.5 A/cm.sup.2 at 77 K. in an applied magnetic field of 0.9 Telsa. The inventive method comprises providing a precursor material whose composition differs from that of the desired superconductor with respect to at least one of the metal constituents of the desired superconductor. It further comprises heating the precursor material above the decomposition temperature (T.sub.d) of the precursor material such that a multiphase material results. The multiphase material comprises, in addition to a majority first phase, a dispersed precipitate phase. The method further comprises cooling the multiphase material to a temperature below T.sub.d at a rate such that at least a major portion of the precipitate phase is retained. The first phase differs from the desired superconductor at most with regard to oxygen content, and the heat treatment of the multiphase material is carried out such that the desired superconductor results. Exemplarily, the desired superconductor is YBa.sub.2 Cu.sub.3 O.sub.7, the precursor material has average composition YBa.sub.2 Cu.sub.4 O.sub.z (z.about.8), the precipitate phase comprises one or more copper oxides, T.sub.d is about 860.degree. C., and the multiphase material is produced at 920.degree. C.
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Jin Sung-ho
Nakahara Shohei
Tiefel Thomas H.
AT&T Bell Laboratories
Bos Steven
Lewis Michael
Pacher Eugen E.
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