Oxygen nonstoichiometry and exchange kinetics of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3 − δ

Abstract

The oxygen nonstoichiometry of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3 − δ (BSCF5582) was investigated by thermogravimetry resulting in values of 2.40 < (3 − δ ) <2.57 for the equilibrium oxygen content in the range 600 ≤ T/°C ≤ 900 and 1E− 4 < pO 2/bar < 0.4. The oxygen exchange kinetics was studied by electrical conductivity relaxation as a function of temperature in the range 550 ≤ T/°C ≤ 725 with chemical diffusion coefficients 1E− 6 < D chem/cm 2 s − 1 < 3E− 5 and surface exchange coefficients 2E− 4 < k chem/cm s − 1 < 3E− 3. The activation energies of the kinetic parameters amount to E a( D chem) = 86 ± 8 kJ mol − 1 and E a( k chem) = 64 ± 12 kJ mol − 1 . Self-diffusion and surface exchange coefficients, as well as ionic conductivities are estimated.