An investigation of non-stoicheiometry in the systems SrFeO3 –y and SrCoO3 –y by iron and cobalt K-edge extended X-ray absorption fine structure spectroscopy

Abstract

A series of samples in the SrFeO_{3 –y}(perovskite and brownmillerite) and SrCoO_{3 –y}(hexagonal and brownmillerite) systems has been studied by extended X-ray absorption fine structure spectroscopy. In the cobalt system, evidence has been found for the existence of face-sharing CoO₆ octahedra in the substoicheiometric low-temperature phase H–Sr₂Co₂O_{5 –x}, and for both face- and edge-sharing CoO₆ octahedra in H–Sr₂Co₂O_{5 +x}. In the iron system, the perovskite phases show only corner-sharing polyhedra, and the short-range structure is seen to be more closely related to the brownmillerite structure.