Oxide superconducting material, process for preparing the same and applications thereof

A process for producing a single crystal of superconducting compound oxide of Tl, Bi, Pb, Sr, Ca and Cu, comprising mixing powders of oxides containing Tl, Bi, Pb, Sr, Ca and Cu in atomic ratios of (Tl+Bi+Pb):

• St:
• Ca:
• Cu=2:
• 2:
• (n-1):
• n, in which "n" is a number between 4 and 7 when Tl/(Bi+Pb)>1 and "n" is a number between 5 and 7 when Tl/(Bi+Pb)=1, melting the oxide powder mixture at 950.degree. to 1,050.degree. C., and then cooling down the resulting melt at a cooling rate of 1.degree. to 20.degree. C./hour.

A process for preparing superconducting material of oxide of Tl, Bi, Sr, Ca and Cu, comprising

• a first sintering step for sintering a first powder material containing Sr, Ca and Cu in atomic ratios of Sr:
• Ca:
• Cu="y":"z":
• "v" in which "y", "z" and "v" are numbers satisfying 0.5.ltoreq.y.ltoreq.3.0, 0.5.ltoreq.z.ltoreq.4.0 and 1.0.ltoreq.v.ltoreq.5.0, and
• a second step for sintering a second powder material which is prepared by adding Tl and Bi to the sintered powder obtained in the first sintering step in atomic ratios of Tl:
• Bi:
• Sr:
• Ca:
• Cu="q(1-x)":
• "xq":
• "y":"z":
• "v", in which "x", "q", "y", "z" and "v" are numbers each satisfying 0.ltoreq.x.ltoreq.1, 0.5.ltoreq.q.ltoreq.3.0, 0.5.ltoreq.y.ltoreq.3.0, 0.5.ltoreq.z.ltoreq.4.0 and 1.0.ltoreq.v.ltoreq.5.0 to obtain the superconducting material containing crystalline compound oxide having a composition represented by the formula:
• (Tl.sub.1-x' Bi.sub.x').sub.q' Sr.sub.y' Ca.sub.z' Cu.sub.v O.sub.w'
• in which x', q', y', z' v' and w' are numbers satisfying 0.ltoreq.x'.ltoreq.1, 0.5.ltoreq.q'.ltoreq.1.5, 1.5.ltoreq.y'.ltoreq.2.5, 1.5.ltoreq.z'.ltoreq.2.5 and 2.5.ltoreq.v'.ltoreq.3.5.

A process for preparing superconducting material of oxide of Tl, Bi, Pb, Sr, Ca and Cu, comprising

• a first sintering step for sintering a first powder material containing Sr, Ca and Cu in atomic ratios of Sr:
• Ca:
• Cu="y":"z":
• "v" in which "y", "z" and "v" are numbers satisfying 0.5.ltoreq.y.ltoreq.3.0, 0.5.ltoreq.z.ltoreq.4.0 and 1.0.ltoreq.v.ltoreq.5.0, and
• a second step for sintering a second powder material which is prepared by adding Tl, Bi and Pb to the sintered powder obtained in the first sintering step in atomic ratios of Tl:
• Bi:
• Pb:
• Sr:
• Ca:
• Cu="q(1-x-p)":
• "xq":
• "pq":
• "y":"z":
• "v", in which "x", "p", "q", "y", "z" and "v" are numbers satisfying 0.ltoreq.x.ltoreq.1, 0.ltoreq.p.ltoreq.0.6, 0.5.ltoreq.q.ltoreq.3.0, 0.5.ltoreq.y.ltoreq.3.0, 0.5.ltoreq.z.ltoreq.4.0 and 1.0.ltoreq.v.ltoreq.5.0 to obtain the superconducting material containing crystalline compound oxide having a composition represented by the formula:
• (Tl.sub.1-x'-p' Bi.sub.x' Pb.sub.p').sub.q' Sr.sub.y' Ca.sub.z' Cu.sub.v' O.sub.w'
• in which x', p', q', y', z' v' and w' are numbers satisfying 0.ltoreq.x'.ltoreq.1, 0.ltoreq.p'.ltoreq.0.6, 0.5.ltoreq.q'.ltoreq.1.5, 1.5.ltoreq.y'.ltoreq.2.5, 1.5.ltoreq.z'.ltoreq.2.5 and 2.5.ltoreq.v'.ltoreq.3.5.