Dislocation Structures of Low‐Angle and Near‐Σ3 Grain Boundaries in Alumina Bicrystals

Alumina bicrystals with low‐angle and near‐Σ3 <0001> tilt grain boundaries were fabricated using diffusion bonding to study the dislocation structures in alumina grain boundaries. The resulting grain‐boundary structures were investigated using high‐resolution transmission electron microscopy, and the grain‐boundary energies were analyzed using theoretical calculations. It was found that partial dislocations with Burgers vectors of the type return ⅓<10[Onemacr]0> were periodically located in the boundaries and that a stacking fault between pairs of partials was formed in such boundaries. The length of the stacking fault decreased with increased misorientation angles, which was reasonably predicted by the theoretical calculation. In the case of a near‐Σ3 grain boundary, an array of displacement shift complete dislocations with the Burgers vector of return ⅓<1[Onemacr]00> was periodically formed along the boundaries. These boundaries did not have stacking faults. The spacing between the dislocations decreased with increased deviation angle from the exact‐Σ3 boundary with the tilt angle of 60°.