Solid oxide electrochemical cell and differential scanning calorimetry used for thermodynamic measurements of the ternary oxides: Nd_2RuO_5(s) and Nd_3Ru_2O_7(s)

摘要

The standard molar Gibbs free energy of formation of Nd_2RuO_5(s) and Nd_3Ru_2O_7(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 Nd_2RuO_5(s) and Nd_3Ru_2O_7(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: {Δ_fG~o(Nd_2Ru_2O_7, s)/(kJ mor~(-1)) ± 1.55} = -2130.29 + 0.4786·(T/K); {Δ_fG~o(Nd_2Ru_2O_7, s)/(kJ mor~(-1)) ± 2.2} = -2501.1 + 0.692·(T/K). Standard molar heat capacity C_(p,m)~o(T) of Nd_2Ru_2O_7(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 Nd_2Ru_2O_(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.