Process for preparing superconducting material

A process for producing a a compound oxide superconductive material represented by the general formula:

• (Ba,Ca).sub.x (.alpha.,Dy).sub.1-x Tl.sub.y Cu.sub.1-y O.sub.3-z
• wherein
• ".alpha." represents Y or La;
• the atomic ratio of Ca to Ba is between 1% and 90%;
• the atomic ratio of Dy to .alpha. is between 1% and 90;
• x, y, and z are within the ranges of 0<x<1, 0<y<1, and 0.ltoreq.z<1 respectively;
• and
• the expression of (Ba,Ca) and (.alpha.,Dy) means that the respective elements occupy predetermined sites in a crystal in a predetermined proportion, said process comprising preparing a material powder, compacting the material powder and then subjecting the resulting compact to a final sintering operation, wherein said material powder is
• (A) a powder mixture composed of
• (i) powders of elemental Ba, Cu, Ca, .alpha., Dy and Tl or
• (ii) powders of compounds each containing at least one of said elements Ba, Cu, Ca, .alpha., Dy and Tl, or
• (iii) a mixture of (i) and (ii),
• (B) a sintered powder obtained by sintering preliminarily the powder mixture (A) and then pulverizing the resulting sintered mass, or
• (C) a powder mixture of said powder mixture (A) and said sintered powder (B),
• in which ".alpha." represents Y or La, and
• wherein, the atomic ratios of (Ba,Ca):
• (.alpha.,DY):Tl:Cu in said material powder are x:(1-x):y:(1-y), the atomic ratio of Ca to Ba is between 1% and 90%, the atomic ratio of Dy to .alpha. is between 1% and 90%, x and y are within the ranges of 0<x<1 and 0<y<1, respectively.