Thermodynamic and Thermophysical Properties of Early Lanthanide Fluorides: LaF ₃ , CeF ₃ , PrF ₃ , NdF ₃ , SmF ₃ , EuF ₃ , and GdF ₃

ABSTRACT Thermodynamic and thermo‐physical properties of fission products play a crucial role in the safe operation of a nuclear reactor. Since, in molten salt rectors (MSRs), lanthanide fluorides will be important fission products, isobaric molar heat capacities ( c p ) of trifluorides of the light lanthanides (LaF 3 , CeF 3 , PrF 3 , NdF 3 , SmF 3 , EuF 3 , and GdF 3 ) were determined experimentally by differential scanning calorimetry, from 303 to 723 K. A simple estimation method was established that could be applied to calculate reliable enthalpies of formation of all lanthanide halides. For the first time, high temperature thermal diffusivities of LaF 3 , CeF 3 , PrF 3 , NdF 3 , EuF 3 , and GdF 3 are reported here, which were measured by laser flash technique from ambient to 1100 K. Thermal conductivities were determined from these values obtained in present study, combined heat capacity data (measured in present work as well as reported in literature) and the geometrically determined densities of the sintered pellets used for thermal diffusivity measurements. Also, the correction was applied to take care of the effect of porosity on the thermal conductivity of the samples, and the corrected thermal conductivities (for nonporous state) of these compounds have been determined in the temperature range starting from 303 up to 1100 K.