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

The high-temperature cubic phase of non-stoichiometric strontium ferrite SrFeOx (2.5 less than or equal to x less than or equal to 3.0) has been studied by in situ neutron powder diffraction in air over the temperature range 300-1273 K. The composition of SrFeOx changes within the range 2.56 less than or equal to x less than or equal to 2.81 from 1273 to 673 K, respectively. Rietveld refinements of the diffraction patterns show that the high-temperature cubic phase of SrFeOx 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 SrFeOx to be described in terms of a solid solution of the composition end members. Cubic SrFeOx at high temperature is found to closely obey Vegard's law. The density of cubic SrFeOx is also found to exhibit a linear relationship with composition. (C) 2002 Elsevier Science Ltd. All rights reserved.