Dislocation structures in a {(1)over-bar104}/⟨11(2)over-bar0⟩ low-angle tilt grain boundary of alumina (α-Al2O3)

An alumina (alpha-Al2O3) bicrystal with a ((1) over bar 104/[11 (2) over bar0] 2(degrees) low-angle tilt grain boundary was fabricated by diffusion bonding at 1500 A degrees 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[(1) over bar 104/[11 (2) over bar <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[<(1)over bar>101] edge component. It is suggested from structural considerations that the dissociated-dislocation pair originates from a b = 1/3[02 (2) over bar1] ->-> 1/6[00 (2) over bar1 +1/6[0 (2) over bar1]) . 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.