The microstructure, liquidus projection and thermodynamic modeling of thermoelectric Ag–Pb–Te system

Ag–Pb–Te is an important system in thermoelectric applications. Various Ag–Pb–Te alloys are prepared and their microstructures are examined. The liquidus projection of ternary Ag–Pb–Te system is determined both by experimental investigations and Calphad calculations, and the results are in good agreement. There are eight primary solidification phases, Ag, γ-Ag2Te, β-Ag2Te, Ag1.9Te, Ag5Te3, Te, PbTe and Pb, including a miscibility gap extended from the Ag–Te side. A ternary-eutectic reaction, L = PbTe + Te + Ag5Te3, was determined with a liquid composition of Ag-4.3at%Pb-62.6at%Te at 337 °C. A nanoscale microstructure containing a dotted PbTe and a lamellar matrix of Ag5Te3 and Te phases results from the ternary eutectic reaction. The solidification paths of selective ternary Ag–Pb–Te alloys are calculated using the Scheil model with the optimized interaction parameters obtained in this study, and the results are consistent with the experimental observations.