Partial Pressures and Thermodynamic Properties for Lead Telluride

The optical absorbance of the vapor over pure Te, over Pb‐Te samples containing 49.01, 49.70, 51.26, and 55 atom percent (a,o) Te, and over a 1.56 mg crystal of is measured between 230 and 700 nm for optical cell temperatures of 1028, 1133, 1273, and 1353 K, and for a range of sample temperatures. The partial pressures of , , and of are extracted from the data. For Te‐saturated , reaches a maximum value of between 1064 and 1099 K and drops to at the 1197 K maximum melting point. increases monotonically with T for Pb‐saturated and is the minimum measurable value of at 1117 K. The partial pressure of , , is determined between 1000 and 1353 K and is at 1197 K. The enthalpy of fusion of deduced from the temperature dependence of . The standard Gibbs energy of dissociation of into Pb(g) and is determined from 1000 up to 1197 K, where it is 79.445 kJ/mol. Combining with the published chemical potentials for Pb and liquidus temperatures for various melt compositions and with published heat capacity data allow a determination of the standard Gibbs energy, enthalpy, and entropy of formation of . At 298 K the latter two quantities are, respectively, and .