Effect of β-Si3N4 seeds on densification and fracture toughness of silicon nitride

Composite materials based on Si3N4 were synthesized by introducing previously prepared β-Si3N4 seeds into a mixture of α-Si3N4 and 10 wt% of sintering additive. The densification process during pressureless sintering was studied in the presence of CeO2 additive, which is less frequently used as sintering aid to Si3N4. The effect of seed concentration and sintering time on the densification and fracture toughness was followed. The results showed that the addition of seeds retarded densification. On the other hand, fracture toughness passes through maximum at the content of 3 wt% seeds.