Fabrication of Si3N4 ceramics with adjustable microstructure and mechanical properties via Y2O3 contents in ZrN-AlN-Y2O3 ternary sintering additives

To adapt to the different application environments, Si3N4 ceramics are required to have different mechanical properties. Therefore, in this study, Si3N4 ceramics with adjustable mechanical properties were fabricated via using ZrN-AlN-Y2O3 ternary sintering additives and hot-pressing at 1650 °C for 30 min. Subsequently, the effect of the Y2O3 concentration on the phase assemblage, microstructure, mechanical properties, and crack propagation of Si3N4 ceramics was systematically investigated. The results demonstrated that Si3N4 ceramics presented adjustable microstructure and mechanical properties with the Y2O3 contents added in the range of 0∼8 wt%. With the increase of Y2O3 contents, the average aspect ratio of Si3N4 grains had an increase of 61.77%, increasing from 3.95 to 6.39. Besides, the Si3N4 grains and the formed YAG intergranular phase exhibited a fairly good combination at the nano-scale. Si3N4 grains and intergranular phase were the main influence factors on the mechanical properties of Si3N4 ceramics. As a result, the bending strength was from 700.99 ± 38.72 to 961.13 ± 36.84 MPa. The fracture toughness exhibited a range of 4.87 ± 0.11 to 6.10 ± 0.23 MPa·m1/2, while Vickers hardness achieved a high level of 16.09 ± 0.16 to 19.98 ± 0.39 GPa.