High temperature enthalpies and heat capacities of YbMnO 3 and YMnO 3

Abstract

Heat capacities of YbMnO 3 and YMnO 3 were measured by differential scanning calorimetry (DSC) from room temperature to 850 K. Enthalpy changes of YbMnO 3 and YMnO 3 were measured by drop calorimeter in the temperature range 573 to 1373 K and heat capacity equations were also estimated. The heat capacity equations were determined by combining the data from both calorimeters and the equations derived for YbMnO 3 from 298 K to 1373 K were Cp,m (J K −1 mol −1)=125.3+11.5×10 −3· T−1.78×10 6· T −2 and for YMnO 3 Cp,m( J K −1 mol −1)=120.8+15.8·10 −3· T−2.41·10 6· T −2. The standard Gibbs free energy changes of formation for YbMnO 3 and YMnO 3 at 298 K were also calculated by using above data. The values were determined to be −1317.6 kJ mol −1 and −1367.1 kJ mol −1, respectively.