An In Situ Study on Phase Relation between Bi2SrO4 and SrCuO2 in the Bi2O3–SrO–CuO System

A pseudobinary phase relation of Bi2SrO4–SrCuO2 in the Bi2O3–SrO–CuO ternary system between 850 and 1100°C has been investigated in situ using an apparatus that combines high-temperature X-ray diffraction with an optical microscopy. The liquidus temperatures increase with decreasing Bi composition from 910°C to 1090°C. The lowest phase change temperature which corresponds to the solidus line of this system is 910°C in the compositions below Bi2Sr4Cu3O10. Above 910°C, the decomposition to Bi4Sr8Cu5O x and liquefaction occurs. On further heating above 925°C, a partially molten phase with solid SrCuO2 appears in the Bi-deficient side. The results are discussed in comparison with stabilities of the Ca-added system of Bi2O3–SrO–CaO–CuO, in which Bi-based cuprate superconductors are formed.