Experimental Evidence for the Development of Bimodal Grain Size Distributions by the Nucleation‐Limited Coarsening Mechanism

It has recently been hypothesized that transient bimodal grain size distributions can arise from unimodal distributions during coarsening if the continued growth of a majority fraction of the crystals is arrested by the energy barrier to nucleate new layers. To test this hypothesis experimentally, SrTiO 3 has been coarsened in a titania‐rich liquid at 1500°C. Measurements of the grain size distribution as a function of time show a transient bimodal distribution that consists of a constant number of larger grains growing many times faster than a decreasing number of much smaller grains. The observations are consistent with the nucleation‐limited coarsening theory, which provides a plausible explanation for the development of transient bimodal grain size distributions in systems of crystals bounded by singular surfaces.