PHASE-RELATIONS AND OXYGEN POTENTIALS IN THE CU-CU2O3-Y2O3 SYSTEM

Phase relations in the Cu"Cu2O3"Y2O3 system were studied by the equilibration and quenching technique. In the temperature range 750-1000°C two cuprates, i.e. Y2Cu2O5 and YCuO2, are stable in the system. The third cuprate, i.e. YCuO3, can only exist at high oxygen pressure. To determine the thermodynamic stabilities of Y2Cu2O5 and YCuO2 the equilibria Y2Cu2O5(s) = 2YCuO2(s) + 1 2O2(g)2YCuO2(s) = Y2O3(s) + 2Cu(s) + 1 2O2(g) were studied by means of solid state e.m.f. measurements. From the data obtained in the temperature range 750-1000°C the following relationships were calculated for the Gibbs energy Y2O3(s) + 2CuO(s) = Y2Cu2O5(s)ΔGf° = -72 579 + 4.24 T J mol-1 1 2Y2O3(s) + 1 2Cu2O(s) = YCuO2(s)ΔGf° = - 32977 + 4.95 T J mol-1. © 1990.