Homogeneity Ranges and Thermodynamic Properties of Ternary Phases in the SnTe-Bi2Te3-Te System

The Sn-Bi-Te system has been studied in the composition region SnTe-Bi2Te3-Te at temperatures from 300 to 430 K using emf measurements on reversible concentration cells of the type. (-)SnTe(s)vertical bar liquid electrolyte, Sn2+vertical bar (Sn - Bi - Te) (s) (+) The subsolidus phase diagram inferred from the emf data includes the ternary compounds SnBi2Te4, SnBi4Te7, and SnBi6Te10 and a broad (0-25 mol % SnTe) range of Bi2Te3-based solid solutions. Best fit equations for the temperature-dependent emf data were used to determine the differences between the partial thermodynamic functions (Delta G) over bar, (Delta H) over bar, (and) (Delta) over barS) of the Sn in SnTe and SnTe-Bi2Te3-Te alloys. From these partial molar functions, we calculated the standard thermodynamic functions of formation and standard entropies of the beta-solution and ternary compounds by integrating the Gibbs-Duhem equation along the SnTe-Bi2Te3 join with the use of the relevant data for SnTe and Bi2Te3.