Thermodynamic studies on LnCoO 3(s) (Ln = Dy, Ho) by solid-state electrochemical cells

Abstract

Ternary oxides, DyCoO 3(s) and HoCoO 3(s) have been synthesized by citrate–nitrate gel combustion method and characterized by X-ray powder diffraction method. The standard molar Gibbs energies of formation of DyCoO 3(s) and HoCoO 3(s) have been measured using solid oxide galvanic cell technique employing yttria-stabilized zirconia (YSZ) and calcia-stabilized zirconia (CSZ) as solid electrolyte tubes, respectively. The standard molar Gibbs energies of formation of DyCoO 3(s) and HoCoO 3(s) were calculated from the measured e.m.f. data and are given as: Δ f G m ° ( DyCo O 3 , s , T ) kJ mo l − 1 ( ± 4 ) = − 1211.3 + 0.2449 ∗ ( T K ) , ( 1013 K ≤ T ≥ 1167 K ) , Δ f G m ° ( HCo O 3 , s , T ) kJ mo l − 1 ( ± 4 ) = − 1237.8 + 0.2590 ∗ ( T K ) . ( 964 K ≤ T ≥ 1102 K ) , A set of self consistent thermodynamic functions for LnCoO 3(s) (Ln = La, Nd, Sm, Eu, Gd, Dy, Ho) has been computed from available experimental data in the literature.