Preparation and properties of Si3N4 ceramics via digital light processing using Si3N4 powder coated with Al2O3-Y2O3 sintering additives

It is difficult to form Si3N4 ceramics by DLP technology owing to the high refractive index and high ultraviolet (UV) absorption of Si3N4 powder. In this paper, the Si3N4 ceramics were successfully fabricated by DLP technology using Si3N4 powder coated with Al2O3-Y2O3 sintering additives. The effects of the coating amount of sintering additives on the properties of Si3N4 ceramic slurry, green bodies and parts after sintering were systematically studied. When Al(NO3)(3) and Y(NO3)(3) solutions were added at a content of 20 mL/100 g Si3N4, 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 mu m) was obtained, the relative density and flexural strength of the Si3N4 ceramics reached maximum values at 85.4% +/- 0.3% and 149.2 +/- 1.9 MPa. The shrinkage of the Si3N4 ceramics remained almost unchanged after coating Al2O3-Y2O3 sintering additives. Finally, the Si3N4 ceramics with excellent quality and clear outline were well prepared. This research has laid a certain experimental basis for DLP forming Si3N4 and other non-oxide ceramics, which is of great researching significance.