Preparation of superconducting-grade copper from commercial grade copper salt

Fine samples with nominal composition of Bi_1·6Pb_0·4Sr₂Ca₂Cu₃O _x have been produced by solid state method using various purity grades of starting copper oxide powder. Studies onT _c and high-T _c volume fraction measurements of these samples revealed that the samples produced using CuO powders obtained in laboratory after double purification of the commercially available copper salts have higherT _c (104·46 K) and increased percentage of highT _c volume fraction (58%) compared to even the samples prepared from Aldrich grade (99·99%) CuO. A simple and cost-effective chemical route for the purification of CuO from commercially available copper salts has been outlined.