In situ neutron diffraction study (300-1273 K) of non-stoichiometric strontium ferrite SrFeO_x

The high-temperature cubic phase of non-stoichiometric strontium ferrite SrFeO_x (2.5 ≤ x ≤ 3.0) has been studied by in situ neutron powder diffraction in air over the temperature range 300-1273 K. The composition of SrFeO_x changes within the range 2.56 ≤ x ≤ 2.81 from 1273 to 673 K, respectively. Rietveld refinements of the diffraction patterns show that the high-temperature cubic phase of SrFeO_x is consistent with a face-centred Fm3c structure. This structure leads to agreement with previous density measurements. This cell allows the high-temperature structure of SrFeO_x to be described in terms of a solid solution of the composition end members. Cubic SrFeO_x at high temperature is found to closely obey Vegard's law. The density of cubic SrFeO_x is also found to exhibit a linear relationship with composition.