Thermodynamic Re-modeling of the Sb-Te System Using Associate and Ionic Models

The Sb-Te system is re-modeled using the calculation of phase diagram (CALPHAD) technique. The liquid phase is modeled as (Sb, Sb₂Te₃, Te) using the associate model and as (Sb³⁺) _p (Te^2?,Te,Va) _q using the ionic model. The solution phases rhom(Sb) and hex(Te) are described as substitutional solutions. Two compounds, delta and gamma, are treated as (Sb)_0.4(Sb,Te)_0.6 according to their homogeneity ranges, while the compound Sb₂Te₃ follows a strict stoichiometry. A set of self-consistent thermodynamic parameters is obtained. Using these thermodynamic parameters, the experimental Sb-Te phase diagram, mixing enthalpies of liquid at 911 K and 935 K, activities of Sb and Te in liquid at 911 K and 1023 K, and Gibbs energy of liquid at 911 K, is well reproduced by the calculations. And the calculated enthalpy of formation, enthalpy of fusion, and heat capacity of Sb₂Te₃ are also in fairly good agreement with all the available experimental data.