Synergistic enhancement of density and curing depth in DLP 3D printed MgO-Y2O3 coated Si3N4 ceramics

The additive manufacturing technology based on digital light processing (DLP) has made it possible to construct silicon nitride (Si 3 N 4 ) ceramics with complex structures. However, due to the high ultraviolet light absorbance and low sintering activity of Si 3 N 4 powders, it is challenging to realize tightly layer bonded and dense Si 3 N 4 ceramics via the DLP technique. Herein, we proposed to coat the Si 3 N 4 particle surface with magnesium oxide and yttrium oxide (MgO-Y 2 O 3 ) layer through the co-precipitation method, in an attempt to achieve the dual purposes of increasing the curing depth and promoting densification. The MgO-Y 2 O 3 layer can not only reduce the refractive index difference between the Si 3 N 4 powder and the photosensitive resin to improve the curing depth, but also serve as the sintering assistance to generate the liquid phase and promote densification. When the coating content of MgO-Y 2 O 3 is 10   wt.%, the curing depth of the ceramic slurry can be increased to 107 μm, which is 33% higher than that of pristine powders. This strategy can provide a simple and effective method to construct advanced Si 3 N 4 ceramics via DLP 3D printing.