Phases ε obtenues par decomposition des spinelles non-stoechiometriques dans les systemes Ga 2O 3-MgO, Al 2O 3-NiO, Al 2O 3-AlN et Al 2O 3-Li 2O

Abstract

In the systems Al 2O 3-AlN, Al 2O 3-NiO, Al 2O 3-Li 2O and Ga 2O 3-MgO, non-stoechiometric spinels, when decomposed at high temperatures, form an intermediate metastable phase ε. This phase has a one-dimensional periodic antiphase-domain structure. The antiphase boundaries are parallel to the (310) plane and the displacement vector is 1 4 [110] when referred to the spinel structure. Across each antiphase boundary, some octahedral and tetrahedral sites share faces instead of corners. In the case of ε AlN, cationic vacancies occupy these sites; in the other cases, this is likely to go along with a segregation of the more charged ions.