Gibbs free energy of formation of a solid Sm2CuBaO5 phase determined by anemf method

First, the Gibbs free energy of formation of the solid CuSmO2 and CuSm2O4 p hases in the (copper + samarium + oxygen) system were determined by employi ng electrochemical cells with zirconia solid electrolyte. The results obtai ned in this study were used to derive the Gibbs free energy of formation of solid Sm2CuBaO5 from the oxides. Next, employing electrochemical cells wit h the single-crystal calcium fluoride as electrolyte: air, CaO + CaF2 \ CaF 2 \ CuSm2O4 + Sm2CuBaO5 + BaF2, air; and air, CaO+ CaF2 \ CaF2 \ CuSm2O4 Sm2CuBaO5 + Sm2O3 + BaF2, air, the Gibbs free energy of formation of solid Sm2CuBaO5 was determined in the temperature range (973 to 1173) K. The resu lts obtained in this study were used to derive the Gibbs free energy of for mation of this phase from the oxides in the following form: Delta(f)G(m)deg rees/(J.mol(-1)) = -110580 + 41.29.(T/K). (C) 1999 Academic Press.