Synthesis and characterization of brownmillerite SrFeO_2.5 in nanostructured form

Synthesis of bulk polycrystalline and nanocrystalline oxygen-deficient SrFeO_2.5 compounds, with potential applications as oxygen membranes, has been explored by chemical route to optimize an easy and reproducible method for high yield. The structure of the samples was investigated by X-ray powder diffraction followed by structural refinement. Both bulk and nanocrystalline SrFeO_2.5 crystallize in Imma space group. X-ray powder diffraction pattern corresponds to the brownmillerite structure in which the Fe cations exist in an octahedral or tetrahedral configuration in alternate layers along the b axis. Brunauer−Emmett−Teller (BET) surface area is found to be 0.40m²/g and 14 m²/g for bulk and nanocrystalline SrFeO_2.5 respectively. The morphology of these materials was also investigated by scanning electron microscopy and transmission electron microscopy