Thermodynamic stabilities of SrCeO3 and Sr2CeO4 using the fluoride EMF technique

The standard Gibbs energies of formation of SrCeO ₃ and Sr ₂CeO ₄ were measured by the EMF method using CaF ₂ as a solid electrolyte. Three fluoride galvanic cells (I–III) were constructed in order to determine Δ _f G ^∘ of SrCeO ₃. The Δ _f G ^∘ of Sr ₂CeO ₄ was determined using galvanic cell (IV). The cells used were (I) Pt , O 2 ( g ) ( 1 bar ) , SrO ( s ) , SrF 2 ( s ) | CaF 2 | SrF 2 ( s ) , CeO 2 ( s ) , SrCeO 3 ( s ) , O 2 ( g ) ( 1 bar ) , Pt (II) Pt , O 2 ( g ) ( 1 bar ) , SrO ( s ) , SrF 2 ( s ) | SrF 2 | SrF 2 ( s ) , CeO 2 ( s ) , SrCeO 3 ( s ) , O 2 ( g ) ( 1 bar ) , Pt (III) Pt , O 2 ( g ) ( 1 bar ) , SrF 2 ( s ) , CeO 2 ( s ) , SrCeO 3 ( s ) | CaF 2 | CaF 2 ( s ) , CaO ( s ) , O 2 ( 1 bar ) , Pt (IV) Pt , O 2 ( g ) ( 1 bar ) , SrO ( s ) , SrF 2 ( s ) | CaF 2 | SrF 2 ( s ) , SrCeO 3 ( s ) , Sr 2 CeO 4 ( s ) , O 2 ( 1 bar ) , Pt The standard Gibbs energy of formation of SrCeO ₃ , derived from the mean of the EMFs of the above galvanic cells (I to III), is given by the following expression: {Δ}_f{G}^∘({SrCeO}₃)±17 (kJ {mol}^-1)=-1703+0.327T (K) (788–1142 K) By combining this expression with the EMF measured using Cell IV, the following expression was obtained for the temperature dependence of the standard Gibbs energy of formation of Sr ₂CeO ₄ {Δ}_f{G}^∘({Sr}₂{CeO}₄)±21(kJ {mol}^-1)=-2307+0.4400 T (K)(805–1066 K)