Si 3 N 4 ceramics were prepared by hot pressing (HP) and spark plasma sintering (SPS) methods using low content (5 mol%) Al 2 O 3 -RE 2 O 3 (RE = Y, Yb, and La)-SiO 2 /TiN as sintering additives/secondary additives. The effects of sintering additives and sintering methods on the composition, microstructures, and mechanical properties (hardness and fracture toughness) were investigated. The results show that fully density Si 3 N 4 ceramics could be fabricated by rational tailoring of sintering additives and sintering method, and TiN secondary additive could promote the density during HP and SPS. Besides, SN-AYS-SPS possesses the most competitive mechanical properties among all the as-prepared ceramics with the Vickers hardness as 17.31 ± .43 GPa and fracture toughness as 11.07 ± .48 MPa m 1/2 .
Silicon nitride (Si 3 N 4 ) ceramics doped with two different sintering additive systems (Al 2 O 3 -Y 2 O 3 and Al 2 O 3 -Yb 2 O 3 ) were prepared by hot-pressing sintering at 1800°C for 2 h and 30 MPa. The microstructures, nano-indentation test, and mechanical properties of the as-prepared Si 3 N 4 ceramics were systematically investigated. The X-ray diffraction analyses of the as-prepared Si 3 N 4 ceramics doped with the two sintering additives showed a large number of phase transformations of α-Si 3 N 4 to β-Si 3 N 4 . Grain size distributions and aspect ratios as well as their effects on mechanical properties are presented in this study. The specimen doped with the Al 2 O 3 -Yb 2 O 3 sintering additive has a larger aspect ratio and higher fracture toughness, while the Vickers hardness is relatively lower. It can be seen from the nano-indentation tests that the stronger the elastic deformation ability of the specimens, the higher the fracture toughness. At the same time, the mechanical properties are greatly enhanced by specific interlocking microstructures formed by the high aspect ratio β-Si 3 N 4 grains. In addition, the density, relative density, and flexural strength of the as-prepared Si 3 N 4 ceramics doped with Al 2 O 3 -Y 2 O 3 were 3.25 g/cm 3 , 99.9%, and 1053 ± 53 MPa, respectively.When Al 2 O 3 -Yb 2 O 3 additives were introduced, the above properties reached 3.33 g/cm 3 , 99.9%, and 1150 ± 106 MPa, respectively. It reveals that microstructure control and mechanical property optimization for Si 3 N 4 ceramics are feasible by tailoring sintering additives.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.