Non-Arrhenius grain growth in strontium titanate: Quantification of bimodal grain growth

Strontium titanate is well-known for its non-Arrhenius grain growth, where grain growth coefficients decrease by orders of magnitude between 1350 °C and 1425 °C. This transition is assumed to be caused by the existence and coexistence of two grain boundary types and results in the formation of bimodal microstructures. So far, no quantified data on the transition behavior was available. The present study uses a comparison of experimental microstructures for various heating times and temperatures with simulated microstructures from phase-field simulations considering various fractions of fast-growing grains. The microstructures are compared by means of their grain size distributions. It is found that the fraction of fast-growing grains follows an anti-Arrhenius behavior. Evaluating the present findings with respective literature data, the grain growth transition could be related to a space charge transition where the fast and slow grain boundaries are associated with strong and weak space charge and segregation. Overall, the present study sheds light on general grain growth transitions observed in several perovskite ceramics