HEAT-CAPACITY MEASUREMENTS ON CATIO3 DOPED WITH CE AND LA

Heat capacity measurements were carried out on (Ca0.85Ce0.15)TiO3 and (Ca0.85La0.15)TiO3 in the temperature range of 292-1550 K by using a d irect heating pulse calorimeter. The results indicate the presence of two phase transitions, one at 1380 +/- 20 K and another at 1540 +/- 20 K in (Ca0.85Ce0.15)TiO3 and one at 1380 +/- 20 K and another above 15 00 K in (Ca0.85La0.15)TiO3. The kind of dopant appeared to have no obv ious difference on the transition temperature. The measured heat capac ity data were used to derive the values of the thermodynamic functions . namely enthalpy increment, entropy and free energy function, as a fu nction of temperature. The enthalpy and the entropy of the phase trans itions: were calculated from the heat capacity change. (C) 1997 Elsevi er Science B.V.