HIGH-TEMPERATURE STABILITIES OF YCUO2, BACU2O2 AND BA2CUO3 FROM OXIDEELECTROLYTE EMF-MEASUREMENTS

The oxygen potentials in the system YCuO2/Y2O3/Cu and Y2O3/YCuO2/CuO w ere measured over the ranges 1113-1255 K and 782-1122 K by employing o xide electrolyte galvanic cells with air/platinum as the reference ele ctrode, and the expression Delta G degrees (f,ox)(YCuO2)(+/- 0.19)(kJ mol(-1)) = -5.346 + 0.00384 T (K) was determined. Similar e.m.f. measu rements were carried out on the electrodes BaCuO2/BaCu2O2/Cu2O and Ba2 CuO3/BaCuO2/BaCu2O2 were measured over the ranges 1003-1132 K and 1175 -1235 K and from the results, the Delta G degrees(f,ox) of BaCu2O2 and Ba2CuO3 were determined to be Delta G degrees(f,ox)(BaCu2O2) (kJ mol( -1)) = -25.09 + 0.01548 T (K) Delta G degrees(f,ox>(BaCu?2O?3)(kJ mol( -1)) = 5.79 - 0.07492 T (K).