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, SrTiO3 has been coarsened in a titania-rich liquid at 15001C. 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.