Abstract
Vapour pressure measurements were carried out over the praseodymium-tellurium samples using a non-isothermal isopiestic method in the temperature range from 764 to 1210 K. From these results, thermodynamic activities of Te were derived as a function of temperature for the composition range ∼65–75 at% Te. This study revealed the existence of non-stoichiometry in the compounds PrTe1.9 and PrTe3. Further, it is found that the thermal stability of PrTe3 is extended beyond 728 K. Using an adapted Gibbs-Helmholts equation, partial molar enthalpies of mixing of Te were obtained for the composition range of PrTe1.9, which was used to convert the activity values of Te to a common average temperature of 1000 K. The relatively large variation of the activity across the homogeneity ranges of the phase PrTe1.9, indicates that it probably belong to the most stable intermetallic compound in this system. Gibbs energies of reaction between selected intermetallic compounds were also determined.
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