Thermodynamic stabilities of SrCeO3 and Sr2CeO4 using the fluoride EMF technique

The standard Gibbs energies of formation of SrCeO3 and Sr2CeO4 were measured by the EMF method using CaF2 as a solid electrolyte. Three fluoride galvanic cells (I–III) were constructed in order to determine ΔfG∘ of SrCeO3. The ΔfG∘ of Sr2CeO4 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 andard Gibbs energy of formation of SrCeO3, 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 + 0.327 T ( K ) ( 788 – 1142 K ) bining 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 Sr2CeO4 Δ f G ∘ ( Sr 2 CeO 4 ) ± 21 ( kJ mol - 1 ) = - 2307 + 0.4400 T ( K ) ( 805 – 1066 K )