High-Temperature Phase Relations and Thermodynamics in the Silver-Tin-Sulfur System

The SnS activities in liquid Ag2S-SnS liquid mattes were obtained at 1100 °C and 1200 °C by the dew-point method. Negative deviations were observed, and the liquid matte solutions were modeled by the Wilson equations. Part of the liquid boundaries of the Ag2S-SnS phase diagram were derived from the model equations, yielding a eutectic temperature of 528 °C at Xsns= 0.38. The phase diagram of the pseudobinary Ag2S-SnS was also verified experimentally by quenching samples equilibrated in evacuated and sealed silica capsules. Solubility limits of the components at the narrow-terminal solid-solution ranges were determined around the eutectic temperature. Within the Ag-Sn-S ternary system, the boundaries of the immiscibility region, together with the tie-line distributions, were established at 1200 °C. Activities of Ag, Sn, and S along the miscibility gap were calculated by utilizing the bounding binary thermodynamics, phase equilibria, and tie-lines.