CRYSTAL-CHEMICAL CHARACTERIZATION OF THE MIXED CONDUCTOR SR(FE, CO)(1.5)O-Y EXHIBITING UNUSUALLY HIGH OXYGEN PERMEABILITY

The crystal chemistry of a recently reported mixed conductor SrFeCo0.5 Oy, exhibiting unusually high oxygen permeability, has been characteri zed by systematically investigating the Sr(Fe, Co)(1.5)O-y system. The samples belong to the general stoichiometry Sr4Fe6-xCoxO13+delta and have an orthorhombic, intergrowth structure isotypic with Sr4Fe6O13 fo r 0 less than or equal to x less than or equal to 1.5. While the inter growth phase Sr4Fe6-xCoxO13+delta and the perovskite phase Sr(Fe, Co)O 3-delta coexist along with CoO impurity for 1.7 less than or equal to x less than or equal to 2.1, the perovskite phase is formed along with CoO impurity for x = 2.4. in the single-phase region with 0 less than or equal to x less than or equal to 1.5, the oxygen content decreases , and the total conductivity increases with x. The occurrence of unusu ally high oxide-ion conductivity is explained on the basis of crystal chemistry.