Crystal structure of the novel complex cobalt oxide Sr0.7Y0.3CoO2.62

The perovskite-related crystal structure of the compound Sr0.7Y0.3CoO2.62 was determined and refined using synchrotron X-ray and neutron powder diffraction, in space group I4/mmm, a = 7.6237(8) Angstrom and c = 15.314(2) Angstrom, to R-I = 0.041 in the synchrotron data set. It contains layers Of CoO6 octahedra, perpendicular to the c axis, alternating with partially disordered oxygen-deficient layers. Further characterization of the structure using electron diffraction and high-resolution electron microscopy showed that an additional superstructure was present in some of the crystallites. The structure represents a new type of layered ordering of oxygen vacancies in oxygen-deficient perovskites. Possible local atom arrangements in the oxygen-deficient layers and the structural relationship to the resembling brownmillerite-type structure for ABO(2.5) compounds are discussed.