Chapter 14. Mechanical Properties of Silicon Carbide Ceramics Densified with Rare-Earth Oxide and Alumina Additions

Summary

Based on the processing strategy of improving the mechanical properties of liquid-phase-sintered materials by tailoring the secondary phase chemistry, four rare-earth oxides (RE₂O₃), La₂O₃, Nd₂O₃, Y₂O₃ and Yb₂O₃, in combination with alumina, were used as sintering aids for a submicron-size β-SiC powder. Doped with 5 vol% RE₂O₃+Al₂O₃ additives, all samples were densified to near theoretical densities by hot pressing at 1800^°C. The phase compositions, microstructures and mechanical properties of the various SiC ceramics were characterized. It was found that a decrease in the cationic radius of the rare-earth oxides was accompanied by an increase in the hardness and flexural strength and a decrease in the fracture toughness of the SiC ceramics.