In this study, two rare earth oxides, Y2O3 and La2O3, are used as the additives in the sintering of
ZrB2-SiC composites to improve the sinterability and control development of microstructure during
densification. The results show that the use of rare earth oxides (5vol.%) improves the powder
sinterability, hindered excessive growth of matrix particles and increase fracture toughness of ZrB2-SiC
composites, in comparison to ZrB2-SiC with additions free. Nearly full dense materials are obtained by
hot pressing at 1900°C. XRD analyses indicate that lanthanum-containing phases were formed in the
composite with La2O3. Microstructure observations by SEM reveal that the grain size of ZrB2-SiC with
Y2O3 and La2O3 composites are less than the sample without additives, which indicates Y2O3 and La2O3
may restrain the grain growth and increase the fracture toughness. The fracture toughness of ZrB2-SiC
composites with Y2O3 and La2O3 reached 5.0MPa·m1/2 and 5.5MPa·m1/2 respectively. Therefore, the
additive Y2O3 and La2O3 are very effective as sintering aids for the ZrB2-SiC composite.
Effect of sintering aids on microstructure and properties of textured SiC ceramics prepared in 6 T