Thermodynamics of indium-tin-oxygen ternary system

A new pyrometallurgical process for the recovery of metallic indium and tin from ITO scrap has been proposed based on the present thermodynamic study on the In-Sn-O ternary system. In the present study the phase relations and the equilibrium partial pressures of oxygen in the ternary system were determined at the temperature of 1173 K. Then by applying the Gibbs-Duhem equation to the phase relation of alloyoxide equilibrium, the activities of the components were obtained at 1173 K using the equilibrium partial pressures of oxygen. Moreover, the vapor pressures of indium and tin were calculated at temperatures of 1173 and 1400 K to discuss the proposed process. The process consists of two stages of reaction: first is the reduction of ITO by CO to In-Sn alloy at a low temperature. Second is the preferential vaporization of indium at a high temperature due to the three orders of magnitude difference between the vapor pressure of indium and that of tin.