The system Yb–Ru–O: High temperature studies on the oxides Yb2Ru2O7(s) and Yb3RuO7(s)

• Electrochemical measurements on solid oxide galvanic cells were carried out for the Yb–Ru–O system.
• Heat capacity was determined using a differential scanning calorimeter.
• Complete thermochemical data was generated for the pyrochlore Yb2Ru2O7(s).

The standard molar Gibbs free energy of formation of Yb2Ru2O7(s) and Yb3RuO7(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 Yb2Ru2O7(s) and Yb3RuO7(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:{ΔfG°(Yb2Ru2O7, s)/(kJ mol−1) ± 1.88} = −2450.4 + 0.6025·(T/K) and{ΔfG°(Yb3RuO7, s)/(kJ mol−1) ± 2.36} = −3109.6 + 0.6202·(T/K).Standard molar heat capacity C°p,m(T) of Yb2Ru2O7(s), was measured using a heat flux type differential scanning calorimeter (DSC) in the temperature range from 307 K to 845 K. The heat capacity of Yb2Ru2O7(s) was used along with the data obtained from the oxide electrochemical cell to calculate the standard enthalpy of formation of the compound Yb2Ru2O7(s), from elements at 298.15 K.