Microstructure and crack resistance behaviour of silicon nitride ceramics

The crack resistance behaviour of two kinds of silicon nitride ceramics which had different microstructure was determined, and the crack closure (bridging) stress distribution in the wake region of the crack tip was also estimated. The results show that the crack resistance is closely related with its microstructure, the R curve of long column shaped β-Si₃N₄ is steeper than that of two phase ceramics βα, meanwhile, the crack closure (bridging) stress distribution in the wake region of the crack tip is also different depending on the different microstructure, therefore the R curve is different.