(0001)LESS-THAN-10(1)OVER-BAR0-GREATER-THAN SLIP AND BASAL TWINNING IN SAPPHIRE SINGLE-CRYSTALS SHOCK-LOADED AT ROOM-TEMPERATURE

The microstructures of sapphire single crystals explosively shocked at pressures of 5, 12, and 23 GPa, with the basal plane perpendicular to the shock wave direction, have been studied using transmission electron microscopy. There was no evidence of microplastic deformation, dislocations or twins, for crystals shocked at 5 GPa. Perfect dislocations with [1010BAR] and 1/3[1120BAR] Burgers vectors on the basal planes were observed at the higher pressures. The gliding of [1010BAR] dislocations on the basal plane established the activation of {0001}[1010BAR] slip, which has not been experimentally verified previously. In addition to dislocation generation and motion, a significant number of basal twins were observed.