Polytype induced exaggerated grain growth in ceramics

In polycrystalline materials we frequently observe exaggerated growth of some grains. One of the reasons for such growth irregularity, which we describe here, is the formation of polytypic sequences within the affected grains. We present an atomic-level study of the polytypic faults that are found in sintered perovskite ceramics with various oxide additions. Grains containing polytypic faults grow preferentially along the direction of fault planes. Results from this study indicate that both the local structure and chemistry of these faults are intimately related to the host crystal and the secondary phase that exists between the main phase and the additive.