Thermal diffusivity of molten CeCl ₃ - <i>M</i> Cl ( <i>M</i> = Li, Na, K, Rb, Cs) mixtures

Thermal diffusivity is a key thermophysical parameter that characterizes the rate of heat propagation through a material under transient thermal conditions. For molten salts, including halide systems, this property is of particular importance for the design and optimization of high-temperature processes. Rare-earth metal halides, such as cerium(III) chloride, are of interest due to their specific structural features and their role as model systems in nuclear technology research. Owing to its electrochemical similarity to plutonium, CeCl₃ is widely employed in experimental studies simulating actinide behavior in pyrochemical processing of spent nuclear fuel. While the thermal diffusivity of pure alkali halides is relatively well studied, the introduction of trivalent cations such as Ce³⁺ leads to significant structural rearrangements in the melt, making direct extrapolation from pure salts unreliable. This work focuses on the thermal diffusivity of binary CeCl₃-MCl (M = Li, Na, K, Rb, Cs) systems over a wide temperature range, using calculated values based on experimental data for thermal conductivity, density, and specific heat capacity. The results reveal a pronounced dependence of the thermal diffusivity on the cationic composition and temperature. The observed trends are interpreted in terms of changes in molar mass, ionic mobility, interionic interaction energies, and structural organization within the melts. The findings provide valuable input for validating molecular dynamics simulations, as well as for developing predictive models of heat and mass transfer in high-temperature applications, including pyrochemical nuclear fuel processing and thermal energy storage systems.