Pressureless sintering of silicon carbide ceramics containing zirconium diboride

SiC-5 wt.% ZrB2 composite ceramics with 10 wt.% Al2O3 and Y2O3 as sintering aids were prepared by presureless liquid-phase sintering at temperature ranging from 1850 to 1950 °C. The effect of sintering temperature on phase composition, sintering behavior, microstructure and mechanical properties of SiC/ZrB2 ceramic was investigated. Main phases of SiC/ZrB2 composite ceramics are all 6H-SiC, 4H-SiC, ZrB2 and YAG. The grain size, densification and mechanical properties of the composite ceramic all increase with the increase of sintering temperatures. The values of flexural strength, hardness and fracture toughness were 565.70 MPa, 19.94 GPa and 6.68 MPa m1/2 at 1950 °C, respectively. The addition of ZrB2 proves to enhance the properties of SiC ceramic by crack deflection and bridging.