title: Strontium superstoichiometry and defect structure of SrCeO3 perovskite.
abstract: Strontium cerate (SrCeO(3)) is the parent phase of a family of prototype proton-conducting perovskites with important potential applications as electrolytes in protonic ceramic fuel cells, hydrogen-separation membranes, and sensors for hydrogen and humidity. Apparent nonstoichiometric behavior and the microstructure of SrCeO(3) have been investigated. Phase analysis by X-ray diffraction indicates that single-phase material in the system Sr(1+x)CeO(3+)delta is obtained for compositions x = 0.02-0.03 and that nominally stoichiometric SrCeO(3) (x = 0) synthesized by either solid-state reaction or the citrate method is Sr-rich. Selected area electron diffraction confirms that the system crystallizes with the GdFeO(3)-type orthorhombic perovskite structure (space group Pnma). Structural defects characterized by high-resolution transmission electron microscopy include twin domain boundaries and SrO-rich, Ruddlesden-Popper-type planar defects. Magnetic susceptibility measurements down to 2 K indicate that the Ce(3+) content is minor ( approximately 0.01 mol per formula unit for slow-cooled material) and does not influence the observed nonstoichiometry.
authors.affiliation: Instituto de CerAmica y Vidrio, CSIC, Cantoblanco, 28049 Madrid, Spain. mather@icv.csic.es
authors.forename: Glenn C
authors.initials: GC
authors.lastname: Mather
authors.forename: Filipe M
authors.initials: FM
authors.lastname: Figueiredo
authors.forename: Julio Romero de
authors.initials: JR
authors.lastname: Paz
authors.forename: Susana
authors.initials: S
authors.lastname: García-Martín