Effect of dislocations on grain growth in strontium titanate

Two series of experiments were done to investigate the effect of dislocatio ns on grain growth in SrTiO3. In the first series, we observed the growth b ehavior of a single-crystal plate toward a TiO2-excess SrTiO3 powder compac t, containing different dislocation densities on two equivalent {100} surfa ces. The surface with a higher dislocation density exhibited faster growth, showing interface mobility enhancement by dislocation, In the second serie s, a polycrystalline SrTiO3 sample which had been plastically deformed by h ot pressing was embedded in a TiO2-excess SrTiO3 powder compact, and its gr owth behavior toward the powder compact was compared with that of a sample without hot pressing. As with a single crystal, the grains with the higher dislocation density in the plastically deformed sample grew faster. In addi tion, some grains in the plastically deformed sample showed the characteris tic of abnormal grain growth. The transmission electron microscopy (TEM) ob servations on a sintered TiO2-excess SrTiO3 showed that the abnormally larg e grains contained many dislocations while the fine matrix grains contained practically no dislocations, This result suggests that the uneven distribu tion of dislocations between grains is possibly one of the causes of the ab normal grain growth in polycrystalline SrTiO3.