Microstructure characterization of hot-pressed β-silicon nitride containing β-Si 3N 4 seeds

Abstract

Self-reinforced silicon nitride ceramics were synthesized by introducing 5 wt% previously prepared β-Si 3N 4 seeds into a mixture of α-Si 3N 4 and 8 wt.% of sintering additive. The microscopic evidence indicates that β-Si 3N 4 seeds play an important role in microstructural development and mechanical properties for silicon nitride ceramics. The growth of β-Si 3N 4 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 Si 3N 4 grains, which were formed to compensate the mismatch and compositional differences between the two grains. Coalescence can occur at the final stage of sintering.