The microstructure of magnesium oxide cleavage surfaces

Abstract

Steps on the cleavage surfaces of MgO single crystals have been examined directly by electron microscopy and x-ray diffraction topography. The geometry of dislocation bands associated with some of the steps indicates that an overlap of cleavage crack segments on different levels occurs prior to step formation. Estimates of the increased elastic energy absorption due to formation of steps of the observed type indicate that this may contribute significantly to the fracture ‘toughness’, particularly for polyerystals.