Equilibrium and kinetic shapes of grains in polycrystals

Impact of AC and DC Electric Fields on the Microstructure Evolution in Strontium Titanate

“…At comparable temperatures and in the absence of electric fields, both orientations have almost the same mobility. [ 49,66 ] However, the present experiments show that both orientations react differently to the oxygen‐vacancy redistribution in electric field: the (100) orientation experiences more increase in the grain‐boundary mobility at the negative electrode.…”

“…Such a setup was used before to characterize the anisotropy of the grain‐boundary mobility. [ 49,66 ] The experiment was done at 1450 °C with 150 V mm −1 and a heating time of 10 h. The obtained growth length is shown in Figure and corresponding representative microstructures in Figure . The field‐free benchmark samples show very homogeneous growth and, as expected, the growth of these two orientations is very similar.…”

“…The field‐free benchmark samples show very homogeneous growth and, as expected, the growth of these two orientations is very similar. [ 49,66 ]…”

“…The difference amounts to a factor of about two, indicating a difference in the grain‐boundary mobility of about due to the parabolic grain growth law. [ 49,66 ] In addition, the layer of enhanced grain growth reaches further into the center of the sample for the (100) orientation compared to (111). At comparable temperatures and in the absence of electric fields, both orientations have almost the same mobility.…”

“…[ 63–65 ] The benefit of such experiments compared to classical experiments is the well‐defined driving force for growth of the single crystal, which allows, for example, an evaluation of the anisotropy of the grain‐boundary mobility. [ 49,65–67 ] Here and in previous studies, [ 6,7 ] this well‐defined driving force was used to experimentally access grain growth gradients as apparent after annealing some functional ceramics in electric field. Such gradients are usually referred to as graded microstructure and grain size between the electrodes and are documented for various materials including alumina, [ 9,10 ] zirconia, [ 68 ] zinc oxide, [ 24,69 ] and barium titanate.…”