Process for preparing superconductor
AssigneeFujitsu Limited
InventorsTakuya Uzumaki, Kazunori Yamanaka, Nobuo Kamehara, Koichi Niwa
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Abstract
Superconductors of the Bi-Pb-Sr-Ca-Cu-O system and Tl-Pb-Ba-Ca-Cu-O system having a high Tc phase (about 110K and about 125K, respectively, or more) at a high proportion are obtained by adding a calcium compound which forms CaO and a liquid phase at a temperature for firing the superconductors, e.g., Ca.sub.2 PbO.sub.x (x=3 or 4); or by starting form a composition represented by the formula: Bi.sub.2 Pb.sub.(n-1)/2 Sr.sub.2 Ca.sub.n Cu.sub.n+1 O.sub.b, or Tl.sub.2 Pb.sub.(n-1)/2 Ba.sub.2 Ca.sub.n Cu.sub.n+1 Ob where 2.ltoreq.n.ltoreq.10, 5.ltoreq.b.ltoreq.40.5, i.e., at a ratio of Ca:Pb=2:1.
Claims16
A process for preparing a superconductor, comprising the steps of:
- preparing a first material, in the form of powder mixture or sintered mass, having a composition represented by the formula (I):
- Bi.sub.u, Pb.sub.v,Sr.sub.w,Ca.sub.x,Cu.sub.y O.sub.z (I)
- where 1.ltoreq.u'3,0.ltoreq.v'.ltoreq.1,1.ltoreq.w'.ltoreq.3,0.ltoreq.x'.ltoreq. 12,1 .ltoreq.y'.ltoreq.12,3.ltoreq.z'.ltoreq.39.5;
- adding to the first material a calcium compound, selected from the group consisting of Ca.sub.2 PbO.sub.4 and Ca.sub.2 PbO.sub.3, and which forms a mixed phase involving CaO and a liquid phase at a temperature not higher than 900.degree. C.;
- and
- firing the resulting mixture of the first material and the calcium compound at a temperature not higher than 900.degree. C. to obtain a superconductor represented by the formula (II):
- Bi.sub.u Pb.sub.v Sr.sub.w Ca.sub.x Cu.sub.y O.sub.z (II)
- where 1.ltoreq.u.ltoreq.3,0.ltoreq.v.ltoreq.1,1.ltoreq.w.ltoreq.2,2.ltoreq.x.lto req.10,3.ltoreq.y .ltoreq.11,6.ltoreq.z.ltoreq.35.
A process for preparing a superconductor, comprising the steps of:
- preparing a first material, in the form of powder mixture or sintered mass, having a composition represented by the formula (III):
- Tl.sub.u,Pb.sub.v,Ba.sub.w,Ca.sub.x Cu.sub.y,O.sub.z, (III)
- where 1.ltoreq.u'.ltoreq.3,0.ltoreq.v'.ltoreq.1,1.ltoreq.w'.ltoreq.3,0.ltoreq.x' .ltoreq.12,1 .ltoreq.y'.ltoreq.12,3.ltoreq.z'.ltoreq.39.5;
- adding to the first material a calcium compound, selected from the group consisting of Ca.sub.2 PbO.sub.4 and ca.sub.2 PbO.sub.3, and which forms a mixed phase involving caO and a liquid phase at a temperature not higher than 900.degree. C.;
- and
- firing the resulting mixture of the first material and the calcium compound at a temperature not higher than 900.degree. C. to obtain a superconductor represented by the formula (IV):
- Tl.sub.u Pb.sub.v Ba.sub.w Ca.sub.x Cu.sub.y O.sub.z (IV)
- where 1.ltoreq.u.ltoreq.3,0.ltoreq.v.ltoreq.1,1.ltoreq.w.ltoreq.2,2.ltoreq.x.lto req.10,3.ltoreq.y .ltoreq.11,6.ltoreq.z.ltoreq.35.
Dependencies are inferred from the claim text.