Partial Pressures and Thermodynamic Properties of PbTe ‐ SnTe Solid and Liquid Solutions with 13, 20, and 100 Mole Percent SnTe

Abstract

The partial pressures of , , and are determined for the solid solutions with and for y values corresponding to Pb‐Sn saturation, to Te saturation, and to compositions within the homogeneity range, as well as for the liquids forming from these solids. The partial pressures are extracted from measurements of the optical absorbance of the coexisting vapor phase between 230 and 700 nm. A number of thermodynamic and phase diagram data are obtained. The enthalpy of fusion of congruently melting, 50.4 a/o Te , is . Combining our data with published data, the high temperature Gibbs energy of formation is obtained for compositions between 50.1 and 50.9 a/o Te and for all of these, and . Comparing our data with 77 K Hall measurements, the native acceptors are doubly ionized for . The Gibbs energy of formation of the solid solutions from the binary compounds is close to, but distinct from, the value for the ideal mixing of and. In contrast the enthalpy and excess entropy of mixing are not closely defined and their 95% confidence level uncertainties include the value zero. The partial pressure of for the 50 a/o Te melts is independent of the x‐value.