Grain-Growth Kinetics of Si3N4 During Alpha-Beta-Transformation

The growth of beta-Si3N4 particles, highly diluted in an oxynitride
glass, was analysed by SEM and the growth features of individual
crystals were discussed. The observed linear time law for the length
growth during alpha/beta-transformation was correlated with results of
a theoretical analysis taking into account the diffusion in the liquid
phase as well as the interface reaction at alpha- and beta-crystals.
The number of initial nuclei was found to be important for a linear
time law of growth. Finally, the considerations of the dilute particle
system were applied to a Si3N4 ceramic. The opposing influence of
growth anisotropy of beta-Si3N4 in the presence of a melt and the
packing requirements demanding a reduction of the specific surface area
is discussed.