Microstructure characterization of hot-pressed β-silicon nitride containing β-Si3N4 seeds

Self-reinforced silicon nitride ceramics were synthesized by introducing 5 wt% previously prepared β-Si3N4 seeds into a mixture of α-Si3N4 and 8 wt.% of sintering additive. The microscopic evidence indicates that β-Si3N4 seeds play an important role in microstructural development and mechanical properties for silicon nitride ceramics. The growth of β-Si3N4 grains is initiated from the seeds, resulting in a core/shell microstructure observed in the abnormal grain growth. The internal dislocation, π-boundary, and Moire fringes are present in Si3N4 grains, which were formed to compensate the mismatch and compositional differences between the two grains. Coalescence can occur at the final stage of sintering.