Abstract: A preparation method for high-purity Tl-based superconductor phase of 115 K, and the precursor thereof. The process comprises a specific composition of precursors, represented by the formula:(Tl.sub.a Pb.sub.b Bi.sub.c)Sr.sub.2-x Ca.sub.2+x Cu.sub.y O.sub.z, wherein (a+b+c)=1, 0<x.ltoreq.1 and 2.ltoreq.y.ltoreq.4, for the manufacturing of Tl-based superconductor by adding oxalic acid as a chelating agent which equals to half the molar amount of total nitrate anions in the required metal nitrates aqueous solution and adjusting pH value of the solution to obtain the superconductor.

Abstract: An oxalate route coprecipitation process for preparing a superconducting YBaCuO system precursor powder comprises preparing an aqueous solution of nitrates of yttrium, barium and copper, which is then mixed with an organic solution containing a dibasic oxalate ester, an organic base and acetone. An ultrasound vibration is applied to the mixture to coprecipitate oxalates of yttrium, barium and copper. The decomposition of the oxalate ester is enhanced to an optimum rate as the result of the homogeneous phase contributed by acetone which is miscible with both water and the oxalate ester. The ultrasound vibration segregates the precipitate particles thereby preventing the coagulation of the particles and assuring fine and uniform particle size.