Prismatic dislocation loops on impurity precipitates in magnesium oxide single crystals

Abstract

Prismatic dislocation loops b = 1/2〈101〉, were observed around impurity precipitates in as-grown magnesium oxide single crystals with a high percentage of Ca and Al impurities. The loops lay on {101} slip planes. By using the results of the dynamical theory of electron diffraction including absorption and stereo microscopy, the majority of the loops were identified as b = 1/2〈101〉 vacancy type. The possible chemical form of these impurities is discussed in view of the nature of the dislocation loops.