PHASE-EQUILIBRIA AND CRYSTAL-CHEMISTRY IN PORTIONS OF THE SYSTEM SRO-CAO-BI2O3-CUO, .2. THE SYSTEM SRO-BI2O3-CUO

New data are presented on the phase equilibria and crystal chemistry of the binary systems SrO-Bi2O3 and SrO-CuO and the ternary system SrO-Bi2O3-CuO. Symmetry data and unit cell dimensions based on single crystal and powder x-ray diffraction measurements are reported for all the binary SrO-Bi2O3 phases, including a new phase identified as Sr6Bi2O9. The ternary system contains at least four ternary phases which can be formed in air at approx. 900°C. These are identified as Sr2Bi2CuO6, Sr8Bi4Cu5O19+x, Sr3Bi2Cu2O8 and a solid solution (the Raveau phase). Superconductivity in this phase apparently occurs only in compositions that correspond to negative values of x. Compositions that lie outside the equilibrium Raveau-phase field often form nearly homogeneous Raveau-phase products. Typically this occurs after relatively brief heat treatments, or in crystallization of a quenched melt.