SiC ceramics strengthened and toughened with a crystallized intergranular phase network structure

Abstract

Covalently bonded silicon carbide (SiC) ceramics exhibit preeminent properties, yet their application scope is still challenged because the low self-diffusivity makes densification difficult. Herein, we use different sintering aids (TiO2, TiO2/Y2O3, and ZrO2/Y2O3) to liquid-phase sinter SiC ceramics. The formation mechanism as well as the microstructure of the intergranular phase (IGP) and the interfacial relation between IGP and matrix grains on the densification and mechanical properties of the material were studied. The results showed that the formed IGP greatly differed in morphology, crystalline nature, and interface structure with the matrix grains. Particularly, fully dense SiC ceramic with a continuous network structure crystallized IGP was fabricated using ZrO2/Y2O3. Benefiting from the proper bonding strength between the IGP and matrix grains, crack deflection took place at the interface between the two, which could enhance the flexural strength and fracture toughness of SiC ceramic up to 725 MPa and 7.27 MPa·m0.5, respectively.