Particle size distribution and dislocation density determined by high resolution X-ray diffraction in nanocrystalline silicon nitride powders

Two silicon nitride powders were investigated by high resolution X-ray diff raction. The first sample was crystallized from the powder prepared by the vapour phase reaction of silicon tetrachloride and ammonia while the second was a commercial powder produced by the direct nitridation of silicon. The ir particle size and dislocation density were obtained by the recently deve loped modified Williamson-Hall and Warren-Averbach procedures from X-ray di ffraction profiles. Assuming that the particle size distribution is log-nor mal the size distribution function was calculated from the size parameters derived from X-ray diffraction profiles. The size distributions determined from TEM micrographs were in good correlation with the X-ray results. The a rea-weighted average particle size calculated from nitrogen adsorption isot herms was in good agreement with that obtained from X-rays. The powder prod uced by silicon nitridation has a wider size distribution with a smaller av erage size than the powder prepared by vapour phase reaction. The dislocati on densities were found to be between about 10(14) and 10(15) m(-2). Publis hed by Elsevier Science S.A. All rights reserved.