Partial pressures of Te2 and thermodynamic properties of Ga–Te system

The partial pressures of Te2 in equilibrium with Ga1−xTex samples were measured by optical absorption technique from 723 to 1373 K for compositions, x, between 0.333 and 0.612. To establish the relationship between the partial pressure of Te2 and the measured optical absorbance, the calibration runs of a pure Te sample were also conducted to determine the Beer’s law constants. The partial pressures of Te2 in equilibrium with the GaTe(s) and Ga2Te3(s) compounds, or the so-called three-phase curves, were established. From the partial pressures of Te2 over the Ga–Te melts, partial molar enthalpy and entropy of mixing for Te were derived and they agree reasonably well with the published data. The activities of Te in the Ga–Te melts were also derived from the measured partial pressures of Te2. These data agree well with most of the previous results except those determined by Predel et al. [Z. Metallkde. 66 (1975) 268]. The possible reason for the high activity of Te measured by Predel et al. [Z. Metallkde. 66 (1975) 268] for x<0.60 is discussed.