Fundamental Material Aspects Underlying the Preparation of High-Temperature Superconducting (Bi,Pb)2+xSr2Ca2Cu3O10+d Ceramics

Phase equilibria of the quasi-quinary system Bi₃O₃-PbO-SrO-CaO-CuO were studied between 650° and 900°C in air with emphasis on the high-temperature superconducting phase (Bi,Pb)_{2+ x} Sr₂Ca₂Cu₃O_{10+ d} (2223). The 2223 phase lies in equilibrium with a number of nonsuperconducting phases and also with the superconducting phase (Bi,Pb)₂Sr₂CaCu₂O_{8+ d} (2212). The single-phase region was found to be very limited. The Pb solubility of the 2223 phase is strongly temperature dependent. The phase relations are very sensitive to variations of the cation concentration and temperature. This effect significantly influences the preparation of 2223 ceramics.