Structure à antiphases périodiques de l'oxynitrure d'aluminium δ₁ non-stoechiométrique de composition 9Al₂O₃–AlN

The ordered non-stoichiometric aluminum oxynitride spinel 9Al₂O₃–AlN has been investigated by X-ray diffraction and electron microscopy. This phase has a one-dimensional periodic antiphase-domain structure. The antiphase boundaries are parallel to the (001) plane and the displacement vector is R = ½〈100〉 when referred to the spinel structure. Periodically spaced clusters of tetrahedral vacancies are grouped in the neighbourhood of each antiphase boundary. These clusters occur in order to avoid an increase in the antiphase-boundary energy, which otherwise would arise, mainly as a result of the Coulomb repulsion between Al³⁺ ions displaced from their normal sites in the spinel lattice adjacent to the boundary.