Thermodynamics of Nonstoichiometric Nickel Tellurides. II. Dissociation Pressures and Phase Relations of Tellurium‐Rich Compositions

Abstract

Dissociation pressures of tellurium over liquid and solid nickel telluride solutions have been measured with a silica Bourdon gauge at compositions corresponding to NiTe1.5, NiTe1.7, NiTe1.9, NiTe2.0, and NiTe9 at temperatures up to 780°. Modifications of the manometric technique are described which permit accuracies of 0.1 mm pressure and 0.1° at high temperatures with corrosive substances where the pressure is sensitive to impurities or to composition changes. The results, together with data on the vapor pressure of pure tellurium, define the partial molal free energies and entropies of tellurium and, together with direct eutectic temperature measurement, delineate features of the phase diagram for compositions with more than 60 atomic percent tellurium.