HIGH-RESOLUTION ELECTRON-MICROSCOPY OF LATTICE-DEFECTS IN TIO2 AND SNO2

High-resolution lattice image observations have been performed for dislocations and deformation twins, introduced by mechanical grinding, in TiO2 and SnO2 crystals with the rutile structure. Dislocations with Burgers vector b = [101] are dissociated into two halves on the (101BAR) plane, while those with b = [001] are not dissociated. Edge dislocations with b = [100] have been found to be dissociated on the (101BAR) plane into a sessile type by the reaction [100] --> 1/2[101] + 1/2[101BAR]. These results are consistent with the relative activities of different slip systems in rutile crystals. An effect of the image force on splitting of dislocations near the foil edge has also been observed. Lattice images of {101BAR} twin boundaries have been compared with the proposed model structure of the boundary. Penetration of a twin through an intersecting twin has been observed.