Abstract
Submicron powders of SiC were synthesized at different temperatures (1700°-2000°C) by reaction of a mixed powder of carbon and silicon dioxide prepared by the spray thermal decomposition method. The structural and quantitative analyses of the synthesized SiC were carried out using the Rietveld method on the basis of the cubic and hexagonal close packed models. The calculated X-ray powder profiles, however, did not coinside with the experimental patterns. The disagreement seemed to be due to the fact that synthesized SiC includes stacking faults. A general method for calculating the X-ray powder profiles by matrices was developed for the quantitative analysis of stacking faults in the SiC structure. The profile calculated on the basis of Paterson model showed that the peak of (102) reflection moved toward the lower angle with increasing amount of stacking faults, which was not observed in the experimental patterns. The present calculation assumed that continuing probability of positive sequence was not the same as that of negative sequence in the Wilson model. The profiles calculated on this model were in good agreement with the experimental patterns, indicating that the structure of the present SiC contained stacking faults in which the proportions of continuing probabilities were different. The values of the positive and negative continuing probabilities decreased as the synthetic temperature increased. The negative probabilitiy was always larger than that of positive one under the present synthetic conditions.
