Crystal Chemical Characterization of the Mixed Conductor Sr(Fe, Co) 5oy Exhibiting Unusually High Oxygen Permeability

The crystal chemistry of a recently reported mixed conductor SrFeCo05O, exhibiting unusually high oxygen permeability, has been characterized by systematically investigating the Sr(Fe, Co)1 Soy system. The samples belong to the general stoichiometry Sr4Fe6_CoO13 and have an orthorhombic, intergrowth structure isotypic with 5r4Fe6013 for 0 x 1.5. While the intergrowth phase Sr4Fe6CoO13+ and the perovskite phase Sr(Fe, Co)O3 _ coexist along with CoO impurity for 1.7 x 2.1, the perovskite phase is formed along with CoO impurity for x = 2.4. In the single-phase region with 0 x 1.5, the oxygen content decreases, and the total conductivity increases with x. The occurrence of unusually high oxide-ion conductivity is explained on the basis of crystal chemistry