High-temperature enthalpy and heat capacity of ErMnO 3

Abstract

The heat capacity of ErMnO 3 was measured by differential scanning calorimetry (DSC) from 300K to about 850K. The heat capacity value at 298K was determined to be 103.7J mol −1 K −1. In order to obtain thermodynamic data at higher temperatures, the enthalpy change of ErMnO 3, H 0 T-H 0 298, was measured in the temperature range 673–1373 K by the drop method. The accuracy of the enthalpy measurement was checked by comparing the measured enthalpy changes of Er 2O 3 and Mn 2O 3 with literature values. The relative error was ± 2% for both compounds. However, for the heat capacity calculated from the enthalpy change, the maximum deviation of the heat capacity from the references was ± 3%. The equation for the heat capacity of ErMnO 3 derived by combining the two methods (DSC and drop methods) was C p = 111.9 + 26.4 × 10 −3 T − 1.33 × 10 6 T −2 from 298 to 1373K. The standard Gibbs free energy of formation for ErMnO 3, − 1362.7 kJ mol −1 at 298K, was also calculated using the above data.