In order to understand vacancy clustering and phase stability in oxygen-deficient barium strontium cobalt iron oxide, stability and activation energies were predicted for oxygen vacancy migration using plane wave density functional theory. Using symmetry-constrained searches and nudged elastic band methods, the transition states were characterized for an oxygen anion moving into a nearby oxygen vacancy site that was surrounded by various cations and the activation energies were found to range from 30 to 50kJ/mol, in good agreement with experimental data. The preference for oxygen vacancies to form square tetramers was confirmed, and found to have a low energy barrier to formation. The presence of Co and Ba cations was found to decrease the activation energy for oxygen vacancy migration. Based on this finding, it was suggested that an increased concentration of these cations would be likely to improve the ionic conductivity and permit the design of solid oxide fuel cells with a reduced operating temperature.

Understanding Oxygen Vacancy Migration and Clustering in Barium Strontium Cobalt Iron Oxide. S.Ganopadhyay, A.E.Masunov, T.Inerbaev, J.Mesit, R.K.Guha, A.K.Sleiti, J.S.Kapat: Solid State Ionics, 2010, 181[23-24], 1067-73