• Optimized Si3N4 slurry formulation achieves 50 vol% solid content with low viscosity (2.48 Pa·s) and excellent stability, enabling high-precision DLP 3D printing.
• Gas-pressure sintering dramatically enhances flexural strength from ~109 MPa to ~618 MPa, while maintaining high hardness (16.59 GPa) and improved fracture toughness (4.45 MPa·m1/2).
• Crack deflection and bridging are identified as dominant toughening mechanisms, along with pull-out of rod-like β-Si3N4 grains, effectively mitigating crack propagation.
• The study provides a pathway for fabricating complex Si3N4 ceramic components with superior mechanical properties via DLP, offering significant potential for advanced engineering applications.