EFFECT OF STACKING-FAULTS ON THE X-RAY-DIFFRACTION PROFILES OF BETA-SIC POWDERS

X-ray diffraction patterns of beta-SiC (3C or the cubic polytype of Si C) powders often exhibit an additional peak at d = 0.266 nm, high back ground intensity around the (111) peak, and relative intensities for p eaks which differ from those predicted from the crystal structure. Com puter simulations were used to show that all these features are due to stacking faults in the powders and not due to the presence of other p olytypes in the powders, Such simulations allow diffraction patterns t o be generated for different types, frequencies, and spatial distribut ion of faults. Comparison of the simulation results to the XRD data in dicates that the beta-SiC particles consist either of heavily faulted clusters distributed irregularly between regions that have only occasi onal faults or twins, or the powders consist of two types of particles with different populations of faults: those with a high density of fa ults and those with only twins or occasional faults. Additional inform ation is necessary to determine which description is correct. However, the simulation results can be used to rule out certain fault configur ations.