Dislocation structures in a {$\bar{1}$104}/〈11$\bar{2}$0〉 low-angle tilt grain boundary of alumina (α-Al₂O₃)

Abstract

An alumina (α-Al₂O₃) bicrystal with a ($\bar{1}$104)/[11$\bar{2}$0] 2^o low-angle tilt grain boundary was fabricated by diffusion bonding at 1500 °C in air, and the grain boundary was observed by transmission electron microscopy (TEM). High-resolution TEM observations revealed that the grain boundary consists of at least two kinds of dislocations. One is a perfect dislocation which has a Burgers vector of 1/3[$\bar{1}$2$\bar{1}$0]. The other is dissociated into two partial dislocations with a stacking fault on the (0001) plane, and each partial dislocation has a 1/6[$\bar{1}$101] edge component. It is suggested from structural considerations that the dissociated-dislocation pair originates from a b = 1/3[02$\bar{2}$1] perfect dislocation (i.e., 1/3[02$\bar{2}$1] → 1/6[02$\bar{2}$1] + 1/6[02$\bar{2}$1]). This dissociation produces a stacking fault in the anion sublattice. The stacking fault energy is estimated to be roughly 1.3 Jm⁻² based on the elastic theory. The authors discuss the dislocation structures and the stacking fault formed on the (0001) plane in detail.