Thermodynamic optimization of the binary PbO–CaO and ternary PbO–CaO–SiO2 systems

Liquidus phase equilibrium data from the recent study for the PbO–CaO and the PbO–CaO–SiO2 systems (as a part of research program on the characterization of the multicomponent PbO–ZnO–FeO–Fe2O3-“Cu2O”-CaO-SiO2 system), combined with phase equilibrium and thermodynamic data from the literature, have been used to obtain a self-consistent set of parameters of the thermodynamic models for all phases: liquid, (Ca,Pb)2SiO4, (Ca,Pb)3SiO5, (Ca,Pb)SiO3 (wollastonite and pseudowollastonite), Pb3(Ca,Pb)2Si3O11 (ganomalite) solutions, SiO2 (quartz, tridymite, cristobalite), Ca3Si2O7 (rankinite), CaO (lime), PbSiO3 (alamosite), Pb2SiO4, Pb11Si3O17, Pb5SiO7 lead silicates, PbO (massicot), Ca2PbO4, Pb8CaSi6O21 (barysilite), PbCa2Si3O9 (margarosanite) and Pb3Ca12Si5O25 compounds. Analysis of available data has shown the lack of data in the two immiscible liquids range over cristobalite, where several new experiments were done to support the model. The modified quasichemical model is used to describe the liquid slag phase. From these model parameters, the optimized ternary phase diagram is back calculated.