Experimental and thermodynamic modeling study of phase equilibria in the Al2O3-SnO-SnO2-SiO2 system

Experimental investigation and thermodynamic modeling of the phase equilibria in the Al 2 O 3 -SnO-SnO 2 -SiO 2 system has been undertaken to characterize Sn behavior in high-Al slags, typical for recycling of waste electrical and electronic materials (WEEE) through black copper process, and the effect of high-Sn slags on Al 2 O 3 -based refractories. Phase equilibria data at 770–1740 °C were obtained through equilibration of synthetic mixtures in sealed silica ampoules, Al 2 O 3 crucibles, on Ir wires, Pt-Ir or Re foils, followed by rapid quenching, and electron probe X-ray microanalysis. Phase equilibria and liquidus isotherms of the Al 2 O 3 -“SnO”-SiO 2 system in equilibrium with Sn metal, Al 2 O 3 -“SnO 2 ”-SiO 2 system in air, and Al 2 O 3 -SnO-SnO 2 -SiO 2 in equilibrium with Au-Sn metal were measured in the quartz/tridymite/cristobalite SiO 2 , cassiterite SnO 2 , corundum Al 2 O 3 , and mullite Al 6+x Si 2-x O 13-0.5x (with minor solubility of Sn 2+ and Sn 4+ ) phase fields. New data were used for developing a thermodynamic database to describe the Pb/Cu-containing complex system for characterizing Sn behavior in industrial primary smelting and recycling slags.