EQUILIBRIUM PHASE-RELATIONS IN THE BI-CA-SR-CU-O SYSTEM AT 850-DEGREES-C AND 900-DEGREES-C

The phase relations of equilibrium compounds in the pseudoternary system Bi2O3-(Ca, Sr)O-CuO at 850 and 900 °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 °C for different durations to ensure that 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 °C, only the superconducting phase, Bi2CaSr2Cu2Ox(2122), was observed inside the triangle. The other stable phases were all positioned on the boundary lines, and included CuO·3/5MO, CuO MO, CuO·2MO, l.l/2Bi2O3·0.9MO, Bi2O3·4MO, Bi2O3·9MO, and a solid solution, Bi2O3·xMO, where 0.16 ≤ x ≤ 0.82 and MO represents l/3(CaO·2SrO). At 900 °C, the above boundary line phases remained stable but the 2122 phase was not observed. The tie lines among the stable phases in the two isotherms were established. © 1990, Materials Research Society. All rights reserved.