COMPOSITIONAL RANGE OF THE BI2SR2CACU2OX HTC-SUPERCONDUCTOR AND ITS SURROUNDING PHASES

The extension of the single-phase field of the two-layer superconductor Bi2Sr2CaCu2O8 is clarified for 830-degrees-C in air. The single-phase field of ''2212'' is a trigonal bipyramid with a length of 13.7 mol% parallel to the SrO-CaO edge, and an extension of 9 mol% perpendicular to it. The tolerance of the lattice concerning CuO variation is smaller than +/- 1.2 mol%. The CaO-rich solid solution is deficient in CuO compared to the ideal 2212 solid solution, Bi2 (Sr1-xCax)3Cu2O8, Whereas the SrO-rich side has excess CuO. Multiphase equilibria around ''2212'' as well as the single phase field were derived by combining the XRD and EDX results of 91 samples of different compositions with the previously published results. The intersections of the multiphase equilibria with three different planar sections of the compositional tetrahedron are shown.