Fabrication of broadband wave-transparent Si3N4 ceramics with octet-truss lattice structure by vat photopolymerization 3D printing technology

Vat photopolymerization 3D printing of Si3N4 ceramics has attracted great attention recently. To overcome the low curing depth limitation caused by alpha-Si3N4, beta-Si3N4 with low absorbance and large particle size was selected in this paper. After printing, the effects of pressureless sintering temperatures on mechanical and dielectric properties were systematically investigated. At 1800 degrees C, the real permittivity of Si3N4 ceramics was 7.37, and the maximum bending strength was 367 +/- 75 MPa. Considering the application of Si3N4 ceramics in radomes/ windows, the dielectric constant of Si3N4 ceramics should be further reduced. Therefore, the octet-truss lattice structure was introduced to optimize the porosity of ceramics. As the porosity increased from 25% to 36%, the real permittivity decreased from 5.56 to 4.42, and the bending strength ranged from 98 +/- 7-62 +/- 13 MPa. It shows that vat photopolymerization 3D printing can be a promising technology for the fabrication of wavetransparent Si3N4 ceramics.