Liquidus projection of the Ag-Sn-Te ternary system

The Ag-Sn-Te ternary system is of interest to thermoelectric applications and its liquidus projection is determined in this study. Forty Ag-Sn-Te ternary alloys are prepared and their primary solidification phases are determined. These different primary solidification phase regions include three terminal solid solutions: Ag, Sn, and Te; six binary intermediate phases: SnTe, β-Ag₅Te₃, Ag_1.9Te, Ag₂Te (assuming no phase transformation), ζ-Ag₄Sn, and ε-Ag ₃Sn; and one ternary compound, AgSnTe₂. These data, together with the phase diagrams of the three constituent binary systems, are employed to construct the univariant lines of the liquidus projection. The temperature-descending directions of these univariant lines are determined using thermal analysis results and mass balance concept. The types of invariant reactions and the reaction temperatures are determined from the temperature-descending directions of the univariant lines and by thermal analysis. There are two Class I reactions, five Class II reactions, and one Class III reaction. The invariant reaction with the highest reaction temperature is L + Ag = Ag₂Te + ε-Ag₃Sn, at 992.7 ± 4K (719.5 ± 4 °C), and that with the lowest reaction temperature is L = Sn + ε-Ag₃Sn + SnTe, at 494.2 ± 4K (221 ± 2 °C).