Transmission electron microscopic studies were performed on lattice defects in 6H silicon carbide single crystals; the crystals being subjected to microhardness indentation tests at between room temperature and 1200C and then to uniaxial compression at temperatures from 1100 to 1650C. It was observed that their basal dislocations, the main defects introduced by deformation, were dissociated into Shockley partials separated by very wide stacking faults; the energy of which was evaluated to be 2.5mJ/m2. The lineshapes of the partials varied considerably, depending upon the sign and angle (with respect to the dislocation line) of the Burgers vector. This suggested that the mobility of the partials was affected by the geometry of the dislocations. The fact that basal dislocations were aligned more or less in crystallographic <11•0> directions indicated the presence of a high Peierls potential. Macroplastic deformation was observed above 1000C. This critical temperature seemed to be determined by the motion of the least mobile partials. The ductile–brittle transition occurred between 800 and 1000C. This transition was considered to have been induced by the temperature-enhanced mobilization of the slowest partials or by the thermally activated constriction of dissociated pairs, both of which were prerequisites for dislocation multiplication. The hardness of the crystals showed a strong temperature dependence below 800C. This was explained by assuming that, although no dislocation multiplication occurs, only very mobile partials experienced thermally activated glide.

Defects in Plastically Deformed 6H SiC Single Crystals Studied by Transmission Electron Microscopy. K.Maeda, K.Suzuki, S.Fujita, M.Ichihara, S.Hyodo: Philosophical Magazine A, 1988, 57[4], 573-92