Fracture of Cr2O3 single crystals on the microscale

Abstract Studying cleavage properties of protective oxide scales is imperative to understand their fracture behaviour, since transgranular fracture is observed in many cases. The small thickness and polycrystalline structure of such scales makes it difficult to identify active cleavage planes directly from mechanical testing. To resolve this issue for Cr2O3, we present an approach to experimentally identify cleavage planes through micro-cantilever bending. Single crystal wafers are used to prepare micro-cantilevers of pentagonal cross-section in different orientations, targeting possible cleavage planes. Fracture surface imaging showed rhombohedral and pyramidal fracture, though surface energy studies predict rhombohedral as the dominant plane. There does exist a preference for rhombohedral fracture over pyramidal, which is also revealed from the experiments.