Oxygen vacancy ordering in SrFe0.25Co0.75O2.63 perovskite material

Abstract

SrFe_0.25Co_0.75O_2.63 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 Sr₃Y₁Co₄O_10.5 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(Fe_0.14³⁺Co_0.36³⁺)₄^8h(Fe_0.11⁴⁺Co_0.14⁴⁺Co_0.25³⁺)₄^8fO_10.52 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.