Determination of the Boundaries of Solid Solutions in the MnTe-Sb2Te3 and SnTe-Sb2Te3 Systems

Abstract

AbstractThe boundaries of stable and metastable states of solid solutions of the MnTe-Sb2Te3 and SnTe-Sb2Te3 systems were determined by solving the thermodynamic equations of phase equilibria using the multipurpose genetic algorithm (MGA). As initial information, we used a small amount of experimental data from DTA and X-ray diffraction analysis, and thermodynamic functions of formation of MnTe, SnTe, Sb2Te3, MnSb2Te4, MnSb4Te7 SnSb2Te4, and SnSb4Sb7 compounds. The temperature-concentration dependences of the Gibbs energy of the formation of solid solutions from binary compounds, as well as from simple substances in quasi-binary sections, were determined using a subregular model of solutions of nonmolecular compounds as applied to telluride systems. The coordinates of the boundaries of metastable and stable solid solutions, in contrast to the entropy, are not very sensitive to the error in determining the enthalpy of formation of binary and ternary tellurides of manganese, tin, and antimony. It was revealed that the boundaries of β (Sb2Te3) solid solutions in MnTe-Sb2Te3 system extend to 10 mol% MnTe, and to 20 mol% SnTe in SnTe-Sb2Te3 system. γ (MnSb2Te4), δ (MnSb4Te7), γ (SnSb2Te4) and δ (SnSb4Te7) solid solutions are stable in the 50–55 mol% Sb2Te3 and 67–72 mol% Sb2Te3 concentration ranges, respectively. Metastable solid solutions areas based on the SnSb2Te4 and SnSb4Te7 compounds have been identified.KeywordsSolid solutionsMnTe(SnTe)-Sb2Te3 systemsThermodynamicsMultipurpose genetic algorithm