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 160A degrees C and 500A degrees 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 160A degrees C. At 500A degrees 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.