Nanocrystalline Transition Aluminas: Nanostructure and Features of X-Ray Powder Diffraction Patterns of Low-Temperature Al2O3 Polymorphs
Physical Review B, Condensed Matter and Materials Physics (up to 2016)
, E-ISSN: 1550-235X
Tsybulya Sergey V.
Kryukova Galina N.
Boreskov Institute of Catalysis SB RAS
Low-temperature -γ, -Ƞ, and χ-Al2O3 polymorphs were studied by high resolution transmission electron
microscopy and x-ray powder diffraction along with computer simulation of the diffraction patterns. Planar
defects lying on the 111, 110, and 100 planes, which are the origin of the broadening of x-ray diffraction
peaks in different forms of aluminium oxide, were revealed. In addition to providing strong experimental
support for the imperfect character of the specimen structures, these results demonstrate the possibility of using
nanosized crystalline domains with a spinel-type arrangement, which are regularly shaped and have a specified,
developed face and bounding surfaces, for the description of the nanostructure of a whole variety of low-temperature Al2O3 derivatives. It was found that different ways of domain packing in the oxide particles with
a subsequent formation of planar defects contribute to specific kinds of line-shape broadening observed in the
x-ray diffraction patterns of these materials. The mechanism of the vacancy generation upon propagation of the
shear-type defect in the 110 plane of the spinel structure, which changes the Al3O4 stoichiometry to Al2O3,
is also discussed.