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 d egrees C and 1200 degrees C by the dew-point method. Negative deviations we re observed, and the Liquid matte solutions were modeled by the Wilson equa tions. Part of the liquid boundaries of the Ag2S-SnS phase diagram were der ived from the model equations, yielding a eutectic temperature of 528 degre es C at chi(SnS) = 0.38. The phase diagram of the pseudobinary Ag2S-SnS was also verified experimentally by quenching samples equilibrated in evacuate d and sealed silica capsules, Solubility limits of the components at the na rrow-terminal solid-solution ranges were determined around the eutectic tem perature. Within the Ag-Sn-S ternary system, the boundaries of the immiscib ility region, together with the tie-line distributions, were established at 1200 degrees C. Activities of Ag, Sn, and S along the miscibility gap were calculated by utilizing the bounding binary thermodynamics, phase equilibr ia, and tie-lines.