Enthalpies of formation of CdSxSe1–xsolid solutions

Abstract

The enthalpies of oxidative drop solution (ΔHds) for a series of CdSxSe1–xsamples were obtained by calorimetry in molten 3Na2O·4MoO3at 975 K. They become more exothermic linearly with increasing S content. The enthalpies of formation from the elements (ΔHf,el) depend linearly on molar ratio of S/(S + Se). This is the first report of thermodynamic properties of CdSxSe1–xsolid solutions measured by any direct calorimetric method. The enthalpies of formation at 298 K from the binary chalcogenide end-members (ΔHf,CdM) (M= S, Se) for wurtzite CdSxSe1–xare found to be zero within experimental errors. These results strongly suggest that wurtzite CdS and CdSe form an ideal solid solution, despite a substantial difference in molar volume and anion radius. This implies that size difference affects thermodynamics less strongly when larger and more polarizable anions are mixed in chalcogenides than when cations are mixed in oxides.