A study of γ-Al2O3 from the viewpoint of 3D nanostructure

In this work, we investigate commercially available γ-Al2O3 oxides with regard to their nanostructure. A deep analysis of high-resolution transmission electron microscopy data as well as total X-ray scattering data, including both Bragg peaks and defect-related diffuse scattering, is performed. The atomistic models of 3D nanostructured γ-Al2O3 nanoparticles are constructed and validated by the Debye function analysis and atomic pair distribution function analysis. It is revealed that the specific defects lying on {100} and {111} planes fragment the γ-Al2O3 nanoparticles into nanosized crystalline blocks. The interblock interfaces are partially coherent because the planar defects locally disturb the cation sublattice and keep anion sublattice intact. The observed shape and mutual arrangement of the primary crystalline blocks are specified by the revealed planar defects. The work shows that the γ-Al2O3 oxides can differ in the density of the defects causing the particle nanostructuring. The proposed models of 3D nanostructure complement the recent crystallographic models of γ-Al2O3 structure by providing further insights into the nature of non-spinel cations. The non-spinel cations are concentrated near the interblock interfaces formed by the planar defects.