Low-temperature heat capacities for EMoO4 (E=Mg, Sr, Ba) substances formed in nuclear fuel waste glasses

Abstract

Thermodynamic properties of various crystalline solids are evaluated from low-temperature heat capacity measurements, in the temperature range 0–300 K using semi-empirical models. Previous studies include fit functions with many coefficients resulting in almost perfect agreement with experimental data. The heat capacities of the end-members of the yellow phase formed in the nuclear fuel waste glasses can be fitted by simple Debye-Einstein integral formula to avoid overfitting. In this study, the heat capacities, the characteristic temperatures (?D,?E1,?E2) and the fitting parameters (m,n1 and n2) of MgMoO4, SrMoO4 and BaMoO4 were determined by fitting the Debye-Einstein integral to the experimental heat capacity. The Debye temperatures ?D of MgMoO4, SrMoO4 and BaMoO4 are 546.15 K, 496.3 K and 420.6 K, respectively, and their Einstein temperatures (?E1,?E2) are (162.46, 1185.25) K, (169.41, 1040.56) K and (125.3, 958.87) K. It is shown from the results that the Debye-Einstein function used in the present study was found to be in good agreement with the experimental data. © 2021