Partial Pressures and Thermodynamic Properties of PbTe ‐ SnTe Solid and Liquid Solutions with 50, 70, and 100 Mole Percent SnTe

Abstract

The partial pressures of , , and have been determined for solid solutions and their melts with , extending earlier studies. The partial pressures were determined from measurements of the optical absorbance between 250 and 700 nm of the vapor phase coexisting with a condensed phase or phases of known composition and temperature. Partial pressures were obtained for the Te‐saturated solid solutions as well as for one composition for that was inside the solid solution homogeneity range. For , the partial pressure of reaches a broad maximum of near 755°C for Te‐saturation and is about at the 851°C solidus temperature. The atomic percent of Te on the Te‐rich solidus line is 50.193 at both 581 and 851°C with an undetermined maximum at an intermediate temperature. The liquidus temperature is 870°C. For , the partial pressure of shows a broad maximum at near 737°C and is at the 834°C solidus temperature. With one exception, the chemical potential of Te relative to Te(l) for SnTe melts between 48.81 and 55.0 atom percent (a/o) Te agree within 7% at 827°C with published values obtained from EMF measurements of the relative chemical potential of Sn. The value for 48.81 a/o Te at 827°C obtained here is higher by 23%. The Gibbs energies of mixing of the solid solutions and their melts is calculated from the partial pressures of and and is close to, but within experimental error, distinct from that for ideal solutions.