V. N. Guskov

Thermodynamic Properties of ZnTe in the Temperature Range 15–925 K

The heat capacity of ZnTe was measured in an adiabatic calorimeter in the temperature range from 15 to 330 K and by DSC at T = 290-925 K. The following standard thermodynamic properties of ZnTe were derived: C 0 p (298.15 K) = (49.52 ± 0.10) J K -1 mol -1 ; S 0 (298.15 K) = (81.94 ± 0.17) J K -1 mol -1 ; H 0 (298.15 K) - H 0 (0 K) = (10.98 ± 0.02) kJ mol -1 ; Φ 0 (298.15 K) = (45.12 ± 0.10) J K -1 mol -1 , Temperature dependences of the heat capacity and the Gibbs free energy function are derived for the temperature range up to 1500 K. The Debye temperature calculated from the specific heat data is Θ D = 252 K.

P–T–X Phase Equilibrium in the Zn–Te System

P-T-X data are the thermodynamic basis for modeling the crystal growth of materials with controlled stoichiometry. In this paper results of the first direct experimental measurement of the total vapor pressure are reported for three-phase equilibria SLV (solid-liquid-vapor) and VLS (vapor-liquid-solid) in Zn-Te, and the P-T projection of the P-T-X phase diagram is constructed. Geometrical analysis of the phase equilibrium showed that three congruent processes are observed in the Zn-Te system: congruent melting (S = L), sublimation (S = V), and vaporization (L = V). All three congruent curves are tangent to SLV. Consequently, all three congruent points are on the Te-side of the maximum melting point of ZnTe. The vapor pressure scanning method was applied to determine the maximum non-stoichiometry as a function of the temperature. The solidus volume of ZnTe was shown to be on the Te-side of the stoichiometric plane.