Microstructure evolution and high-temperature mechanical properties of porous Si3N4 ceramics prepared by SHS with a small amount of Y2O3 addition

Abstract

Porous Si3N4 ceramics with well-developed microstructure and high flexural strength were successfully prepared by self-propagating high temperature synthesis (SHS) using a small amount of Y2O3 as sintering additive. Influences of Y2O3 content on the phase composition, microstructure evolution, flexural strength at both room temperature and elevated temperature of ~1400 °C and their fracture behavior of the obtained porous Si3N4 ceramics were investigated. Porous Si3N4 ceramic with high average aspect ratio of 4.03 and excellent flexural strength of 101 MPa was obtained by 0.4 wt% Y2O3 addition. It also shows good strength retention of 76.6% and evidently elastic fracture behavior at 1400 °C because of its rather low amorphous intergranular phase content. With the increase of Y2O3 content, the creep resistance of sample degraded owning to the softening of amorphous intergranular thus resulting in the degradation of high-temperature strength retention.