Thermodynamic functions of thorium–cerium mixed oxides

Abstract

Thorium–cerium mixed oxides (Th1−xCex)O2 (x = 0.25, 0.5, 0.75) were prepared by the citrate gel combustion technique. X-ray diffraction investigations of these samples revealed the formation of single-phase (fluorite) solid solutions. Heat capacity and enthalpy increments of these samples were measured by using a differential scanning calorimeter and a drop calorimeter (MHTC 96) in the temperature range 298–800 K and 523–1723 K, respectively. The values of heat capacity in the temperature range 523–1800 K were computed from the enthalpy increment data. With the help of these data, analytical expression for the heat capacity of (Th1−xCex)O2 (x = 0.25, 0.5, 0.75) as well as entropy and Gibb’s energy functions were obtained. The heat capacity values at 298 K pertaining to (Th1−xCex)O2 (x = 0.25, 0.5, 0.75) were found to be 64.92, 64.80, and 64.27 J K−1 mol−1, respectively. The thermodynamic functions are being reported for the first time.