GRAIN-GROWTH KINETICS OF SI3N4 DURING ALPHA-BETA-TRANSFORMATION

The growth of beta-Si3N4 particles, highly diluted in an oxynitride gl ass, was analysed by SEM and the growth features of individual crystal s were discussed. The observed linear time law for the length growth d uring alpha/beta-transformation was correlated with results of a theor etical analysis taking into account the diffusion in the liquid phase as well as the interface reaction at alpha- and beta-crystals. The num ber of initial nuclei was found to be important for a linear time law of growth. Finally, the considerations of the dilute particle system w ere applied to a Si3N4 ceramic. The opposing influence of growth aniso tropy of beta-Si3N4 in the presence of a melt and the packing requirem ents demanding a reduction of the specific surface area is discussed.