High-temperature enthalpy of praseodymium selenides in the homogeneity range bounded by Pr3Se4 and Pr2Se3

Calorimetry is used to study the enthalpy of the bounding compositions Pr3Se and Pr2Se3 of the Pr3–xSe4 phase (0 ≤ x ≤ 1/3) at 450–2300 K. The temperature–concentration dependences of the thermodynamic properties of Pr3–xSe4 selenides in the homogeneity range are determined at 298 ≤ T ≤ 2156 K. The Pr3–xSe4 enthalpy function has the following form: H(T, x) − H(298 K, x) = (2817 ⋅ 103T−1 − 75912 + 234.6 ⋅ T − 4.718 ⋅ 10−2T2+ 2.624 ⋅ 10−5 T3) ⋅ e−0.2086x J/mole. An analysis of the partial enthalpies of Pr and Se shows that the chemical bonds between these elements change in simple substances and Pr3–xSe4.