Standard Gibbs free energy of formation of BaCuO 2 and BaCu 2O 2 from oxides

Abstract

Phase relations in the CuCuOBaO system were studied by the equilibrium and quenching technique. In the temperature range 800–950°C three cuprates, i.e. BaCuO 2, Ba 3CuO 3 and BaCu 2O 2, are stable in the system. The thermodynamic stabilities of BaCuO 2 and BaCu 2O 2 were determined by means of the e.m.f. measurements for the following equilibria: BaCu 2 O 2( s) = BaO( s) + 2 Cu( s) + ( 1 2 ) O 2( g) and 2 BaCuO 2( s) + Cu 2 O( s) = 2 BaCu 2 O 2( s) + ( 1 2 ) O 2( g) . From the data obtained on these three-phase combinations the following relationships were calculated for the Gibbs free energy: BaO(s) + Cu 2O(s)=BaCu 2O 2(s) with ΔG f o = −30358 + 0.90 T (J mol −1); and BaO(s) + CuO(s) = BaCuO 2(s) with ΔG f o = −42900 + 7.8 T (J mol −1).