VACANCY ORDERING IN GAMMA-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 gamma-Fe2O3. Powder diffraction data as well as high-resolution electron microscopy show that the basic structure of gamma-ferric oxide possesses cubic symmetry (space group P4(3)32), whereas the ordered distribution of the cation vacancies on the octahedral positions results in the formation of the tetragonal superlattice (space group P4(1)2(1)2). The character of the superstructure orientation with respect to the developed planes of the gamma-Fe2O3 microcrystals obtained by different preparative techniques is also discussed.