Vat photopolymerization 3D printing of high-performance Si3N4 ceramics through synergistical optimization of slurry formulation and sintering kinetics

Si 3 N 4 ceramics have great potential for applications in mechatronics, biomedical implants and other advanced industries. 3D printing such as vat photopolymerization (VPP) helps the fabrication of highly complex-shaped ceramics that have not been possible with conventional manufacturing methods. However, the primary challenge is the poor dispersion and high light absorption of Si 3 N 4 powder, which leads to high slurry viscosity and limited printability. This study presents a comprehensive strategy for fabricating high-performance Si 3 N 4 ceramics via VPP by synergistically optimizing slurry formulation and sintering kinetics. We systematically engineered a 50 vol% solid loading slurry by identifying the optimal content of dispersant as 2 wt% of solid powder and the photoinitiator as 3 wt% of resin, achieving an excellent balance of low viscosity (2.58 Pa·s at 30 s −1 ) and enhanced curing depth (69 µm). The core innovation lies in uncovering the critical role of sintering heating rate on the final microstructure and properties. A detailed investigation of four heating rates (5–0.5 °C/min) at 1600°C revealed that the slowest rate (0.5 °C/min) is paramount. It promoted superior densification (64.67% relative density), controlled anisotropic shrinkage, and significantly increased three-point bending strength to 209.67 ± 2.51 MPa, a 95% improvement over the fastest rate. The work establishes that coupled optimization of rheology, curing, and most importantly, sintering thermal profile is essential for unlocking the full mechanical potential of VPP-fabricated Si 3 N 4 , providing a validated blueprint for high-performance, complex-shaped ceramic components.