Experimental Liquidus Study of the Binary PbO-CaO and Ternary PbO-CaO-SiO2 Systems

Phase equilibria of the binary PbO-CaO and ternary PbO-CaO-SiO2 systems have been investigated at 870-1655 degrees C for oxide liquid in equilibrium with air and solid oxide phases: tridymite or cristobalite SiO2, pseudowollastonite CaSiO3, dicalcium silicate (Ca,Pb)(2)SiO4, tricalcium silicate (Ca1-xPbx)(3)SiO5 (x<0.03), new phase tricalcium-lead silicate (Ca0.8Pb0.2)(3)SiO5 (Ca12Pb3Si5O25), lime CaO, and calcium plumbate Ca2PbO4, covering the ranges of concentrations not studied before. High-temperature equilibration on primary phase or inert metal (platinum, gold) substrates, followed by quenching and direct measurement of the Pb, Ca and Si concentrations in the phases with the electron probe x-ray microanalysis (EPMA) has been used to accurately characterize the system. Liquidus phase equilibrium data of the present authors for the PbO-CaO-SiO2 system are essential to obtain a self-consistent set of parameters of thermodynamic models for all phases.