Growth of single crystalline seeds into polycrystalline strontium titanate: Anisotropy of the mobility, intrinsic drag effects and kinetic shape of grain boundaries

We present a suite of measurements and combined analyses of grain growth in SrTiO3 for oriented single crystals into polycrystals. The growth distance and standard deviation and the microstructure evolution along the single crystal-matrix interface are used to locally characterize the change in migration behavior as a function of temperature, time and interface orientation. The relative grain boundary mobility was determined between 1250 degrees C and 1600 degrees C for four crystallographic orientations (100), (110), (111) and (310). An absolute mobility of these orientations is estimated. Under fast growth conditions the morphology of single crystals shows macroscopic stepping with parts of the interface rotating to low mobility orientations. This effect represents a kinetic influence on the grain boundary morphology. The results also indicate dragging effects on microstructure coarsening, which indicate the existence of a critical driving force for grain growth. This critical driving force seems to be related to an 'intrinsic' interface drag similar to the solute drag, but based on intrinsic defects. At 1460 degrees C the growth of single crystals was significantly faster than expected from the mobility of the polycrystal and was identified as exaggerated grain growth. The findings give new insights into the recently published grain growth anomaly of strontium titanate, leading to a hypothesis based on the temperature dependent relative mobility of (100) oriented grain boundaries. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.