Solid oxide electrochemical cell and differential scanning calorimetry used for thermodynamic measurements of the ternary oxides: Nd2RuO5(s) and Nd2Ru2O7(s)

Abstract

The standard molar Gibbs free energy of formation of Nd2RuO5(s) and Nd2Ru2O7(s) was determined using an oxide solid-state electrochemical cell wherein calcia stabilized zirconia (CSZ) was used as an electrolyte. The standard molar Gibbs free energy of formation of Nd2RuO5(s) and Nd2Ru2O7(s) from elements in their standard state was calculated by the least squares regression analysis of the data obtained in the present study and can be given respectively by: {ΔfGo(Nd2RuO5, s)/(kJ mol−1) ± 1.55} = −2130.29 + 0.4786·(T/K); {ΔfGo(Nd2Ru2O7, s)/(kJ mol−1) ± 2.2} = −2501.1 + 0.692·(T/K).Standard molar heat capacity Cop,m(T) of Nd2Ru2O7(s) was measured using a heat flux type differential scanning calorimeter (DSC) in two different temperature ranges, from 127 K to 299 K and 307 K to 745 K. The heat capacity of Nd2Ru2O7(s) was used along with the data obtained from the oxide electrochemical cell to calculate the standard enthalpy and entropy of formation of the compound from elements at 298.15 K.