Equilibrium phase diagrams for the systems PbO–SrO–CuO and PbO–CaO–SrO

In order to obtain essential information on the formation process of the high-T_c phase in the Bi, Pb–Sr–Ca–Cu–O system, subsolidus phase equilibrium in the systems PbO(PbO₂)–SrO–CuO and PbO(PbO₂)–CaO–SrO has been studied, mainly by XRD analysis. A pseudoternary Pb–Sr–Cu–O solid solution was newly found. This solid solution has a wide solubility range including its typical composition Pb_2.03Sr₃Cu_0.73O_7.70. It has a hexagonal structure with lattice parameters a = 10.11 and c = 7.11 in AU. Composition dependences of the lattice parameters and the decomposition (incongruent melting) temperature of (Ca_1−xSr_x)₂PbO₄ solid solution are also reported.