Phase relation of equilibrium compounds in the Bi-Ca-Sr-Cu-O system

The phase relations of equilibrium compounds in the pseudoternary system Bi2O3-(Ca, Sr)O-CuO at 850 and 900 degrees C were studied. The ratio of Ca:Sr was fixed at 1:2. Starting materials of Bi2O3, CaCO3, SrCO3 and CuO with various ratios were mixed, pressed into pellets, and heated at or above and then brought back to 850 or 900 degrees C for different durations to ensure that the equilibrium had been reached. The products were cooled in air or quenched in liquid nitrogen and then identified by x-ray powder diffraction. At 850 degrees C, only the superconducting phase, Bi2CaSr2Cu2Ox(2122), was observed inside the triangle. The other stable phases were all positioned on the boundary lines, which included CuO · 3/5MO, CuO · 0.9MO, and a solid Bi2O3 · 4MO, Bi2O3 · MO, where 0.16 ≤ x ≤ 0.82 and MO represents 1/3(CaO · 2SrO). At 900 degrees C, the above boundary line phases remained stable but the 2122 phase was not observed