Investigation on thermophysical properties of RE6UO12(s) (REÂ =Â La, Pr, Nd, Sm)

RE6UO12(s) (RE = La, Pr, Nd, Sm) was synthesized by citrate-nitrate combustion method. The synthesis condition for Pr6UO12(s) was optimized. Nonstoichiometry in these rare earth uranates in argon atmosphere was analysed using various techniques like thermogravimetry (TG), X-ray photo electron spectroscopy (XPS), chemical analysis and electrical conductivity measurements. Thermal expansions of RE6UO12(s) (RE = Pr and Sm) was studied in the temperature range 298-1273 K by high temperature X-ray powder diffractometry and compared with that of similar rare earth compounds reported in the literature. Heat capacity of RE6UO12(s) (RE = La, Pr, Nd, Sm) was measured by differential scanning calorimetry in the temperature range 300-870 K. Enthalpy, entropy and Gibbs energy functions of these compounds were computed from the measured heat capacity data.