Enthalpy and heat capacity of (Ca 1− xPu x)TiO 3 ( x=0 and 0.20)

Abstract

Enthalpy increment measurements on (Ca 1− x Pu x )TiO 3 ( x=0 and 0.20) were carried out at temperatures between room temperature and 1180 K by the drop method using a high-temperature Calvet micro-calorimeter. The enthalpy increment values were given for CaTiO 3 and (Ca 0.80Pu 0.20)TiO 3 in polynomial expressions of temperature using Shomate's method. Heat capacity equations obtained in this study were used to derive the thermodynamic functions, namely entropy and free energy function, and to determine the thermodynamic formation values, namely the standard molar enthalpy of formation, the standard molar Gibbs free energy of formation and the standard molar entropy of formation. The Gibbs free energy of formation of (Ca 0.80Pu 0.20)TiO 3 was smaller than that of CaTiO 3 in the temperature range from room temperature to 1200 K, showing that (Ca 0.80Pu 0.20)TiO 3 is thermodynamically more stable than CaTiO 3. The thermodynamic stability of CaTiO 3 was found to increase by means of Pu substitution for Ca in CaTiO 3.