Effect of TiB₂ on properties and microstructure of Si₃N₄‐TiB₂ ceramics sintered at lower temperature

Si 3 N 4 is a low thermal expansion, high‐performance structural ceramic that is widely used in extreme environments. However, the excessively high sintering temperatures required for densification limit further applications and the improvement of mechanical properties. In the present study, a high‐performance Si 3 N 4 ‐TiB 2 ceramic was fabricated at a lower sintering temperature. The effect of TiB 2 content, sintering temperature, and holding time on the microstructure, mechanical properties, grain size distribution, and fracture surface energy of the ceramic was systematically investigated. The results showed that the TiB 2 addition primarily improves the ceramic's properties by reducing the porosity defects and improving the densification and grain boundary adhesion strength. When the TiB 2 content is 9 Vol%, the Si 3 N 4 ‐TiB 2 ceramic exhibits optimal mechanical properties. The Vickers hardness, fracture toughness, and flexural strength were 16.7 ± 0.3 GPa, 8.0 ± 0.15 MPa·m 1/2 , and 655 ± 13 MPa. In addition, the TiB 2 addition can reduce the densification temperature of Si 3 N 4 ‐TiB 2 ceramic, enhance the densification of the ceramic, refine the grain structure, improve the grain distribution of the Si 3 N 4 ‐TiB 2 ceramic, and notably improve the material hardness and fracture toughness. The toughening mechanisms in the Si 3 N 4 ‐TiB 2 ceramic are the synergistic effects of crack deflection, transgranular fracture, grain pull‐out, and grain bridging.