Microstructure and Mechanical Performance of Silicon Nitride Ceramics with Seeds Addition

With Y2O3:Al2O3 of different weight ratios as sintering additives and 3wt% β-Si3N4 seeds addition, sili- con nitride ceramics were prepared by gas pressure sintering. The phase composition, density, microstructure, room temperature as well as elevated temperature mechanical properties were investigated. The experimental results in- dicated that the α→β phase transformation of silicon nitride would be finished at 1800℃ for 2 h, and the densities of all specimens were over 97% of theoretical density. Compared with the specimen without seeds addition, the room temperature bending strength, the elevated temperature flexural strength at 1200℃ and the fracture toughness of the specimen with 6wt%Y2O3-4.5wt%Al2O3 and 3wt% β-Si3N4 seeds addition can be improved by 20%, 16% and 8%, respectively.