Short‐Cut BN Fiber‐Toughened Wave‐Transparent Si ₃ N ₄ Ceramics Prepared by Vat Photopolymerization 3D Printing Process

Si 3 N 4 ceramics are widely applied in mechanical and electronic engineering fields owing to their superior high‐temperature resistance, strength, and hardness. However, inherent brittleness and high dielectric constant limit their usage in high‐temperature wave‐transparent devices. To overcome this, BN fibers (BN f , the main component is hBN) with high aspect ratio and mechanical stability were, for the first time, directly incorporated into a Si 3 N 4 matrix via vat photopolymerization 3D printing process as toughening phases, designed to enhance stress transfer and suppress crack propagation. The effects of BN f content, sintering temperature, and holding time on microstructure and properties were systematically investigated. At an optimal condition (1800°C, 4 h, 4 vol% BN f ), the ceramic showed an open porosity of 28.79%, bending strength of 136 ± 9 MPa, fracture toughness of 2.92 MPa·m 1/2 , and dielectric constant of 4.28. This work provides methods and theoretical guidance for the design and manufacture of directly incorporated fiber‐toughened high‐temperature wave‐transparent materials.