Preparation and Properties of Si3N4 Ceramics via Digital Light Processing Using Si3N4 Powder Coated with Al2O3-Y2O3 Sintering Additives

It is difficult to form Si 3 N 4 ceramics by DLP technology owing to the high refractive index and high ultraviolet (UV) absorption of Si 3 N 4 powder. In this paper, the Si 3 N 4 ceramics were successfully fabricated by DLP technology using Si 3 N 4 powder coated with Al 2 O 3 -Y 2 O 3 sintering additives. The effects of the coating amount of sintering additives on the properties of Si 3 N 4 ceramic slurry, green bodies and parts after sintering were systematically studied. When Al(NO 3 ) 3 and Y(NO 3 ) 3 solutions were added at a content of 20 mL/100 g Si 3 N 4 , the slurry with lowest viscosity (0.042 Pa·s at a shear rate of 30 s −1 ) and a higher monolayer curing depth (47.9 ± 1.2 µm) was obtained, the relative density and flexural strength of the Si 3 N 4 ceramics reached maximum values at 85.4% ± 0.3% and 149.2 ± 1.9 MPa. The shrinkage of the Si 3 N 4 ceramics remained almost unchanged after coating Al 2 O 3 -Y 2 O 3 sintering additives. Finally, the Si 3 N 4 ceramics with excellent quality and clear outline were well prepared. This research has laid a certain experimental basis for DLP forming Si 3 N 4 and other non-oxide ceramics, which is of great researching significance.