Experimental and thermodynamic modeling study of phase equilibria in the ZnO–SnO–SnO ₂ –SiO ₂ system

Abstract Experimental investigation and thermodynamic modeling of the phase equilibria in the ZnO–SnO–SnO 2 –SiO 2 system have been undertaken to characterize Sn behavior in the high‐Zn slags for recycling of waste electrical and electronic materials (WEEE) through the black copper process. Phase equilibria data at 870–1746°C were obtained through equilibration of synthetic mixtures in sealed silica ampoules or open crucibles, on Ir wires, Pt, Pt‐Ir, Mo, and Re foils, followed by rapid quenching, and electron probe X‐ray microanalysis. Phase equilibria and liquidus isotherms of the ZnO–“SnO”–SiO 2 system in equilibrium with Sn metal, ZnO–“SnO 2 ”–SiO 2 system in air, and ZnO–SnO–SnO 2 –SiO 2 in equilibrium with Au–Sn metal were measured in the quartz/tridymite/cristobalite SiO 2 , cassiterite SnO 2 , zincite ZnO (with minor solubility of SnO 2 ), willemite Zn 2 SiO 4 , and spinel Zn 2 SnO 4 phase fields.