Thermodynamic properties of SrRuO3(s)

The enthalpy increment measurements and the standard molar Gibb's energy of formation of SrRuO3(s) were measured using a high-temperature Calvet micro-calorimeter and a galvanic cell, respectively. The enthalpy increments can be represented by the polynomial expression: H0(T)-H0(298.15 K) (J mol-1)=-43517.2+120.8T (K)+0.898×10-2T2 (K)+19.97×105/T (K) [SrRuO3(s), 310.4&leT (K)&le798.8]. The heat capacity C0p,m(T), the first differential of H0(T)-H0(298.15 K) with respect to temperature is given by: C0p,m (SrRuO3, s, T) (J mol-1 K-1)=120.8+1.796×10-2T (K)-19.97×105/T2 (K). The standard Gibbs energy of formation of SrRuO3(s) has been determined by a galvanic cell using CaF2(s) as the solid electrolyte. The fluoride cell is represented by: (-)Pt/O2(g), {CaO(s)+CaF2(s)}//CaF2//{SrF2(s)+RuO2 (s)+SrRuO3(s)}, O2(g)/Pt(+). The electromotive force (emf) of the above cell was measured as a function of temperature in the range from 894.4 to 1098 K. The standard Gibb's energy of formation of SrRuO3(s) from elements in their standard state obtained by the fluoride cell can be given by: ΔfG0[SrRuO3(s)]/kJ mol-1(±2)=-941.0+0.2586&middot(T/K) (894.4av=996.2 K. The heat capacity of SrRuO3(s) determined by Calvet calorimeter and the data obtained from fluoride cell were used to calculate the standard enthalpy and entropy of formation of the compound at 298.15 K. The second law method gives ΔfH0[SrRuO3(s), 298.15 K] and ΔfS0[SrRuO3(s), 298.15 K] of the compound from elements in their standard state to be -955.0 kJ mol-1 and 111.04 J K-1 mol-1, respectively. © 2002 Elsevier Science B.V. All rights reserved.