Phase equilibria study of Cu-O-ZnO system in various oxygen partial pressures

Phase relationships of the Cu-O-ZnO system in equilibrium with air (P_O2=0.21 atm) and metallic copper (in pure argon) have been studied for the first time using equilibration/quenching/EPMA techniques. In this study, we quantified the phases in equilibrium with air in the temperature range 1095-1500 °C and represented the equilibria by the pseudo-binary phase diagram (Cu₂O-ZnO). The diagram has one simple eutectic reaction with two primary phases of cuprite (Cu₂O) and zincite (ZnO), and the binary eutectic point was found to be 1098±2 °C with 0.10±0.01 mol fraction of ZnO. There were three phases Cu₂O+ZnO+liquid copper or ZnO (Cu₂O)+liquid oxide+liquid copper coexisting with each other in the temperature range 1205-1300 °C, when the system was equilibrated with metallic copper. Isothermal ternary phase diagrams (Cu-O-ZnO) were used to present the results of the experiments at Cu saturation. The eutectic point of the Cu saturated system was determined to be 1208±2 °C and 0.03±0.01 mol fraction of ZnO. Results were compared with the phase diagrams calculated by MTDATA 5.10 and its Mtox 7.0 database. The differences between the experimental data and the computational phase boundaries were significant and the system properties require a re-assessment.