Effects of Sc2O3 sintering aid for the densification and mechanical properties of SiC-ZrB2 composites

This study examined the effects of a Sc2O3 sintering aid on the density, microstructure and mechanical properties of SiC-5 vol% ZrB2 composites prepared by hot-pressing. Microstructural studies showed that the addition of Sc2O3 not only caused a decrease in the hot-pressing temperature from 1950 to 1750 °C by liquid phase sintering, but also resulted in the formation of crystalline Sc4Zr3O12 at the grain boundaries via a reaction with ZrO2 on the surface of the ZrB2 powder. The addition of Sc2O3 produced a fine-grained microstructure with a 43% (430→615 MPa) and 20% (3.6→4.3 MPa m1/2) increase in flexural strength and fracture toughness, respectively, compared to the SiC-ZrB2 composite without Sc2O3.