Abstract:The phase equilibria of the PbO-“CuO_0.5” and PbO-“CuO_0.5”-“FeO_1.5” slag systems in equilibrium with solid metallic copper and/or liquid metallic lead-copper alloy were studied as part of the investigation of the 19-element PbO-ZnO-Cu₂O-FeO-Fe₂O₃-CaO-SiO₂-Al₂O₃-MgO-S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co as minor elements) multicomponent slag/matte/metal/speiss system, supporting the operation and development of the existing and emerging pyrometallurgical processes. In the experimental portion of this study, samples underwent high temperature equilibration followed by quenching, after which the compositions in the liquid slag, solid oxide and metallic phases were directly measured by electron probe microanalysis (EPMA). Phase equilibria data on the massicot (PbO), spinel ((Fe,Cu)Fe₂O₄), cuprite (Cu₂O), lead ferrite (Pb_2+xFe₂O_5+x), magnetoplumbite (Pb_1+xFe_12-xO_19-x), copper plumbite (Cu₂PbO₂), and delafossite (CuFeO₂) primary phase fields were obtained between 688 and 1000 °C. A key finding of the experimental study of the PbO-“CuO_0.5” subsystem was that the copper plumbite (Cu₂PbO₂) phase melted incongruently, contradicting previous studies that suggested it apparently decomposed below the binary eutectic temperature to form massicot (PbO) and cuprite (Cu₂O). Based on the results of past and present experimental studies, a self-consistent set of thermodynamic model parameters describing all phases in the system was derived using the FactSage software package.

Key words: lead oxide; copper oxide; iron oxide; phase diagram; liquidus; slag; metal; phase equilibrium