Phase Equilibria of the Sn-Bi-Te Ternary System

Bi₂Te₃ is one of the most promising thermoelectric materials, and Sn is the primary constituent of most electronic solders. Knowledge of phase equilibria of the Sn-Bi-Te ternary system is important for thermoelectric applications. Twenty-seven Sn-Bi-Te alloys were prepared and equilibrated at 160°C and 500°C. The equilibrium phases were determined, and the isothermal sections were constructed based on three binary constituent phase diagrams and ternary phase equilibria results. No ternary compounds were observed in the Sn-SnTe-Bi region. The SnTe phase is very stable and has tie-lines with the Sn, liquid, and Bi phases at 160°C. At 500°C, in addition to the already known SnBi₂Te₄ and SnBi₄Te₇ ternary phases, two new ternary compounds (Sn₂Bi₂Te₅ and SnBiTe₂ phases) were found. SnTe and Bi₂Te₃ have significant mutual solubilities, and the ternary compounds SnBi₂Te₄, SnBi₄Te₇, and Sn₂Bi₂Te₅ are all in the SnTe-Bi₂Te₃ pseudobinary section.