Abstract
Residual strain and atomic structures in the vicinity of the grain boundaries were investigated for (2310)[0001] Σ21, (4510)[0001]Σ7 and (0112)[2110]RΣ7 symmetrical tilt grain boundaries of Al2O3 bicrystals using convergent beam electron diffraction (CBED) and high-resolution electron microscopy (HRTEM). CBED measurement clearly showed that the RΣ7 grain boundary has a relatively small strain across the boundary. On the other hand, there is strain of about 0.06-0.07% in the area 10 nm from the grain boundaries in both the Σ21 and Σ7 grain boundaries. It was found that signs of strain distribution in the vicinity of the grain boundary observed in the Σ21 specimen were opposite to those observed in the Σ7 specimen. The interplanar distances of (2110) a-plane and (0001) c-plane in the Σ21 boundary were confirmed to increase and decrease, respectively, in the vicinity of the grain boundary. In contrast, the respective interplanar distances in the Σ7 boundary decrease and increase, respectively. The difference in the change of interplanar distance observed in the Σ21 and Σ7 boundaries is considered to be closely related to the atomic density at the respective grain boundaries.
