Oxygen vacancy ordering in SrFe 0.25 Co 0.75 O 2.63 perovskite material.

SrFe0.25 Co0.75 O2.63 was synthesized by a solid-state reaction. Its structural study at room temperature using conventional X-ray as well as neutron powder diffraction, electron diffraction and high-resolution transmission electron microscopy is presented. An oxygen-vacancy ordering related to the "314" model known for the Sr3 Y1 Co4 O10.5 oxide is proposed despite neither an A-site ordering nor an A-site mismatch. By means of Mössbauer spectroscopy, Mohr salt titration and the difference in the neutron cross sections of Fe and Co, a cation distribution within the crystallographic sites as the following Sr4 (Fe0.14 3+ Co0.36 3+ )4 8h (Fe0.11 4+ Co0.14 4+ Co0.25 3+ )4 8f O10.52 is suggested, highlighting a natural layered structure with Fe and Co in higher oxidation states in the oxygen replete layers than in the oxygen deficient ones.