SYNTHESIS OF (BI,PB)(2)SR2CA2CU3OZ SUPERCONDUCTING PHASES FROM VARIOUS PRECURSORS

Bi1.6Pb0.4Sr2Ca2Cu3Oz superconducting materials were prepared by react ing lead oxide or presynthesized lead-containing compounds (Ca2PbO4, B i1.6Pb0.4CuOz) with Sr-Ca-Cu-O oxides in which the Sr : Ca : Cu ratios were adjusted to those of 2223, 2212, and Sr1-xCaxCuOz. We also prepa red Bi1.65Pb0.35Sr1-yCayCu2Oz (y = 1.0, 1.5, 1.9) materials and examin ed their reaction with heat-treated and unheat-treated mixtures of oxi des and carbonates taken in amounts corresponding to the overall stoic hiometry of 2223. The content of 2223 was determined from x-ray diffra ction measurements, and the volume fraction of superconductivity was e valuated from magnetization data. To assess the critical parameters, w e also recorded the resistive transition. Long-term firing yielded nea rly single-phase 2223 materials with C-s = 60 +/- 5% and T-cf = 99-104 g. The use of precursors was found to accelerate formation of 2223 in comparison with the synthesis from simple oxides and carbonates.