Vacancy Ordering in γ-Fe₂O₃: Synchrotron X-ray Powder Diffraction and High-Resolution Electron Microscopy Studies

This paper reports synchrotron X-ray powder diffraction and high-resolution electron microscopy studies of the structural arrangement in γ-Fe₂O₃. Powder diffraction data as well as high-resolution electron microscopy show that the basic structure of γ-ferric oxide possesses cubic symmetry (space group P4₃32), whereas the ordered distribution of the cation vacancies on the octahedral positions results in the formation of the tetragonal superlattice (space group P4₁2₁2). The character of the superstructure orientation with respect to the developed planes of the γ-Fe₂O₃ microcrystals obtained by different preparative techniques is also discussed.