Transient Liquid Phase Sintering of Silicon Nitride by Hafnia Addition

Effect of HfO sub 2 addition on densification behaviors and microstructures of sintered products in the Si sub 3 N sub 4 -Y sub 2 O sub 3 -AlN system was investigated. In the HfO sub 2 doped specimens, the crystallization of the grain boundary phases was promoted. The densification was enhanced by the HFO sub 2 addition, especially in the range of 1-1.5 wt.% < 1800 deg C. The densities of the specimens fired at 1850 and 1900 deg C increased with increasing HfO sub 2 content. It was confirmed that the crystallization promotion of the grain boundary phases occurred in the high temperature firing of the specimens with HfO sub 2 addition, which was not observed in without HfO sub 2 . This phenomenon suggested that the full densification and the crystallization in this system were carried out through the transient liquid phase sintering.