Thermodynamic stability and impedance measurements of perovskite LuRhO3(s) in the Lu–Rh–O system

Abstract

The Gibbs energy of formation of LuRhO₃(s) has been determined using a solid-state electrochemical technique employing an oxide ion conducting electrolyte. The Gibbs energy of formation of LuRhO₃(s) from elements in their standard state calculated from the data obtained can be represented by: {Δ_fG^o(LuRhO₃, s)/(kJ mol⁻¹) ± 1.35} = −1164.3 + 0.2685(T/K) (943 ≤ T/K ≤ 1121). The standard enthalpy of formation and entropy of the compound at 298.15 K has been derived following the second law method. The standard molar heat capacity of LuRhO₃(s) was determined from 128 K to 846 K using a heat flux type differential scanning calorimeter. Based on the thermodynamic data for the compound, an oxygen potential diagram for the Lu–Rh–O system was computed. Impedance measurements on LuRhO₃(s), suggests a semiconductor like behavior with low activation energy.