Structures and thermodynamics of some rare earth sulfides

The vaporization behavior of the Nd-S and Yb-S systems was studied at 1952 - 2229 K and 1688 - 1842 K respectively. The congruent vaporizing compounds found in both systems are nonstoichiometric compounds, i.e., NdS(1.38) and Yb(0.877)S. The equilibrium partial pressures of the gaseous species, the second- and third-law enthalpies and entropies of the vaporization reaction were obtained. Two new thulium sulfides: Tm8S11 and Tm15S22 were discovered by vaporization of Tm-S samples using the Knudsen effusion method. Single crystals of both compounds were obtained and their structures were solved by single crystal x-ray diffraction techniques.