2005 Volume 113 Issue 1316 Pages 325-329
High-temperature characteristics (especially high-temperature strength and oxidation resistance) of gas pressure sintered Si3N4 ceramics using Yb2O3-SiO2 additives were evaluated. The high temperature characteristic of Si3N4 depended on the Yb2O3/SiO2 molar ratio of additives. High 1500°C bending strength of 395 MPa was obtained for sintered bodies with 10.0 mass% addition of additives with Yb2O3/SiO2 molar ratio of 1.0. Also, small weight change (13.2 g/m2) during oxidation at 1300°C for 300 h was obtained in this sintered body. This is considered to be due to the precipitation of Yb4Si2N2O7 and Yb2Si2O7 phase in the grain boundary glass phase, as induced by a crystallization process.