Structures of dissociated 〈1over(1, ̄) 0 0〉 dislocations and {1over(1, ̄) 0 0} stacking faults of alumina (α-Al₂O₃)

An alumina (α-Al₂O₃) bicrystal with a {1over(1, ̄) 0 0}/〈1 1over(2, ̄) 0〉 2° low-angle grain boundary was fabricated by diffusion bonding, and the grain boundary was observed by high-resolution transmission electron microscopy (HRTEM). It was found that 1/3〈1over(1, ̄) 0 0〉 partial-dislocation triplets were periodically arrayed along the boundary. The atomic structure within the {1over(1, ̄) 0 0} stacking faults in between the partial-dislocation triplets was determined by HRTEM combined with first-principles calculations. We discuss the stacking fault structures and their excess energies in detail.