Microstructure and mechanical properties of pressure‐less sintered B₄C–SiC–ZrB₂–LaB₆ ceramic composites

The effect of LaB 6 on the densification and microstructure of pressure‐less sintered 0.4B 4 C–0.4SiC–0.2ZrB 2 ternary ceramic with eutectic composition was investigated. The Vickers hardness, bending strength, and fracture toughness of the quaternary ceramic were discussed based on the microstructural characteristics. The densification of the 0.4B 4 C–0.4SiC–0.2ZrB 2 ceramic was enhanced with increasing LaB 6 content from 0 to 70 mol% (the proportion to B 4 C–SiC–ZrB 2 ). When the LaB 6 content was 50 mol%, the densification rate of the composite ceramic reached a peak. The 0.27B 4 C–0.27SiC–0.13ZrB 2 –0.33LaB 6 quaternary composite ceramic has reached a density of over 95% after being sintered at 2 100°C for 1 h. The B 4 C and SiC phases had refined grains of 1–3 µm with intragranular structures in the as‐sintered ceramics. The hardness and strength reached 17.9 ± .8 GPa and 307 ± 38 MPa, respectively. Crack deflection and branching were ascribed to the improved fracture toughness of 3.78 ± .26 MPa·m 1/2 . This study provides new ideas for fabricating dense non‐oxide ceramic composites with enhanced properties.