Integrated experimental phase equilibria study and thermodynamic modeling of the PbO-SnO-SnO2-SiO2 system in air and in equilibrium with Pb-Sn metal

Phase equilibria of the PbO-SnO-SnO2-SiO2 slags with solid phases (cristobalite, tridymite and quartz SiO2, cassiterite SnO2, massicot PbO, lead stannate Pb2SnO4, and lead-tin silicate Pb3Sn2SiO9) were studied at 800-1730 degrees C in air and in equilibrium with Pb-Sn metal. High-temperature equilibration on silica, platinum or platinum-iridium foil, or on MgO substrates, followed by quenching and direct measurement of Pb, Sn and Si concentrations in the phases using electron probe X-ray microanalysis (EPMA) was used to accurately characterize the system. Present experimental data were used to obtain a self-consistent set of parameters of the thermodynamic models for all phases in this system using FactSage computer package. The modified quasi chemical model with two sublattices (Pb2+, Sn2+, Sn4+, Si4+)(O2-) was used for the liquid slag phase, while all solid phases were described as stoichiometric. A detailed review was done to reevaluate the properties of SnO and SnO2 slag endmembers and the melting point of cassiterite in air. Present study was a part of research program on the characterization of the multicomponent Pb-Zn-Cu-Fe-Ca-Si-O-S-Al-Mg-Cr-As-Sn-Sb-Bi-Ag-Au-Ni system. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The phase equilibria of PbO-SnO-SnO2-SiO2 slags were studied through high-temperature equilibration and electron probe X-ray microanalysis, providing accurate characterization of the system. Parameters of the thermodynamic models for all phases were obtained, and a detailed review was conducted to reevaluate the properties of SnO and SnO2 slag endmembers.