Sintering shrinkage behavior and mechanical properties of HfO2-added Si3N4 ceramics

HfO(2)-added Si(3)N(4) ceramics are known to exhibit excellent high-temperature strength and excellent damage characteristics because HfO(2) assists the crystallization of the grain boundary phase. However, the sintering shrinkage behavior and mechanical properties of HfO(2)-added Si(3)N(4) have not been well clarified so far, although it has been reported that TiO(2), in which Ti is from the same group as Hf in the periodic table, enhances the densification of the Si(3)N(4)-Y(2)O(3)-Al(2)O(3)-AlN system and wear resistance due to TiN formed from TiO(2) and AlN in the grain boundary. In the present study, we focus on HfO(2) as the sintering aid to investigate the sintering shrinkage behavior and mechanical properties of HfO(2)-added Si(3)N(4). The powder mixtures are prepared by the addition of HfO(2) to the Si(3)N(4)-Y(2)O(3)-Al(2)O(3) or Si(3)N(4)-Y(2)o(3)-Al(2)O(3)-AlN system. The sintering shrinkage curves of HfO(2)-added Si3N4 ceramics show rapid shrinkage at 1600 degrees C as compared with those of the Si(3)N(4) ceramics without HfO(2). The shrinkage can be explained by the formation of Sio(2)-Y(2)O(3)-HfO(2) derived liquid phases. Furthermore, the mechanical properties of HfO(2)-added Si(3)N(4) were as excellent as those of the Si(3)N(4) ceramics without HfO(2).