The fabrication, mechanical property and oxidation of Si3N4 ceramics with rare earth oxide addition

The effects of rare earth oxide(Lu2O3) on the property, microstructure and oxidation behavior of hot-pressing sintered Si3N4 ceramics were investigated. The silicon nitride ceramics with Lu2O3 as addition have been fabricated by hot-pressing at 1800 degrees C for 1 h under a pressure of 25 MPa. Oxidation test was carried out at 1400 degrees C in air for 100 h with TGA measurement. Mechanical properties, SEM and XRD were measured before and after oxidation. The results showed that Si3N4 ceramics doped Lu2O3 have good microstructure and mechanical properties. Oxidation test showed a parabolic weight gain with oxidation time at 1400 degrees C in air and the oxidation products of the ceramics were SiO2, Lu2Si2O7 and Lu2SiO5 confirmed by XRD and SEM and EDS. The rate-control ling step is the diffusion of ion. The samples showed superior oxidation resistance to those from the literature.