Abstract
Thermal transformation of SiC crystals were studied experimentally. Needle-like 2H crystals prepared by the gaseous cracking method were heated up to 1, 200-2, 300°C, and when brought down to room temperature, their X-ray oscillation photographs were taken. Diffuse streaks appeared along the c*-direction in the diffraction pattern of the specimen heated at 1, 600°C, and then spots due to 3C emerged along the streaks. At 1, 900°C, spots due to 4H appeared and at 2, 000°C those due to 6H. The spots from 3C disappeared at 2, 100°C. Throughout these changes, the external form of the specimen remained unchanged and most part of 2H persisted. At 2, 300°C, only spots observed were those from 2H and 6H. From these findings, it was concluded that 3C, 4H, 6H and probably 2H are thermodynamically stable phases, and their relative amounts were estimated at each temperature. The mechanism of the transformations was believed to be due to the periodic slip process, and stacking disorder was confirmed to be the sole phenomenon premonitory of the transformations and capable of lowering the extremely high potential barriers attached to these transformations.
