Grain growth in perovskites: What is the impact of boundary transitions?

Several perovskite ceramics are known to have non-Arrhenius type grain growth and to show grain
growth transitions instead. These growth transitions are coupled to bimodal microstructures and seem
to be caused by the existence, coexistence and transition of two different grain boundary types. This
paper gives a review on the details of the grain growth transitions in perovskite ceramics. A simple mean
field approach and standard grain growth experiments are used for quantification. However, this
approach is far too simple to understand bimodal anisotropic grain growth completely as apparent in
perovskites. Important parameters such as atomistic boundary structure, segregation effects, wetting
transitions, faceting, grain boundary stoichiometry, space charge and interfacial drag effects are discussed
with respect to their impact on grain growth in perovskites. A summary of open questions and future
directions is given.