10 KBAR PHASE-EQUILIBRIA IN THE Y-BA-CU OXIDE SYSTEM AT 950-DEGREES-C

Phase equilibria in the YO1.5BaO-CuO system have been determined at 95 0 degrees C at 10 kbar using a piston-cylinder apparatus. The oxide ph ases stable under these conditions are Y2O3, Y2Cu2O5, CuO, Y2BaCuO5, Y Ba2Cu3O6.5, BaCuO2, Y2BaO4, Y2Ba3O6, and YBa4Cu2O7.5. The phase stabil ities observed at 950 degrees C at 10 kbar are identical to those obse rved at 950 degrees C in air or oxygen at 1 atm for compositions with <40% Pa of the cations. In more Ba-rich portions of the phase diagram, carbonates and oxycarbonates are stabilized and a systematic determin ation of the phase equilibria has not been successful.