Identification of the space group and detection of cationic ordering in iron antimonate using conventional and convergent-beam electron diffraction

Abstract

The structure of rutile-related iron antimonate, FeSbO₄, has been determined by electron diffraction. It is shown, in agreement with earlier studies by X-ray diffraction, that the space group is P4₂/mnm. However, and in distinct contrast to the conclusions drawn from the X-ray diffraction data and more recent neutron diffraction studies which have described the structure of the compound in terms of the random distribution of iron and antimony over the cationic sites in the oxygen octahedra, it is shown here that the iron and antimony ions are ordered such that c≈ 9.23 Å as opposed to 3.07 Å determined by X-ray diffraction. The extent of cationic ordering appears to be influenced by the nature of the cationic oxidation states. The means by which the structure of small,ca. 200 Å diameter, particles of iron antimonate have been determined by electron-diffraction techniques is presented in detail to demonstrate the value of such methods for the structural examination of inorganic solids.