Silicon Nitride Joining Using Silica and Yttria Ceramic Interlayers

Abstract

Dense hot-pressed β-Si 3 N 4 blocks were joined using both SiO 2 and SiO 2 -Y 2 O 3 powder slurries as bonding interlayers. The assembled specimens (Si 3 N 4 /interlayer/Si 3 N 4 ) were heated in a flowing N 2 atmosphere in the temperature range of 1500°-1650°C. The joining interlayer was clearly distinguished from the Si 3 N 4 bulk. The microstructure and the reaction products found in the bonding interlayer were very different in both compositions. Reactions occurring between the Si 3 N 4 and the ceramic joining compositions have been explained based on existing diagrams of the YN-Si 3 N 4 -Y 2 O 3 -SiO 2 system.