ON BASAL SLIP AND BASAL TWINNING IN SAPPHIRE (α-Al_20_3)--I. BASAL SLIP REVISITED

摘要

The motion of partial dislocations (b = 1/3[0110> and 1/3[1010>)‖ during basal slip ((0001) 1/3 <1120>) in sapphire (α-Al_20_3) is analysed. Crystallographic arguments suggest that the basal slip plane should be a plane passing through the normally-vacant octahedral sites defined by the anion sublattice. This definition of the basal slip plane implies that half of the cations lying between two adjacent anion layers are above and the other half are below the slip plane. The stacking faults that would be created by the motion of a dissociated basal dislocation differs in structure and energy, depending on whether the 1/3[1010> partial is leading or trailing.