X-RAY STUDIES ON SYNTAXIC COALESCENCE PHENOMENON OF POLYTYPES IN SiC
碳化硅多型体连生现象的X射线研究

By means of the Laue X-ray diffraction method the distribution of polytypes, rule and characteristic features of syntaxic coalescence, and crystal perfection of 400 silicon carbide single crystals, which were taken from graphite furnace and induction furnace of 32 experimental runs and from industrial furnace, have been studied. Numerous observations demonstrate that parallel coalescence in plate silicon carbide single crystal is a very common phenomenon. The crystals with coalescence of more than two polytypes amount to about 2/3 of the crystals studied, whereas crystals of the single type amount to only 1/3. Sometimes coalescence consists of even above 4-5 polytypes.The analysis of polytype distribution in furnace indicates that the polytypes are distributed irregularly, and different polytypes may be found even at the same place of one furnace. The relations among polytype, colour, and etching figure in SiC are analysed. Finally, the different mechanisms of polytype formation in silicon carbide suggested up to date are discussed.