Particle grading strategy for optimizing mechanical and dielectric properties of 3D FSS ceramic substrates fabricated via digital light processing

Wave-transparent ceramic based three-dimensional frequency selective surfaces (3D FSS) offer broader bandwidth and improved angular stability compared to their two-dimensional counterparts. The fabrication of periodic and complex-shaped 3D FSS using low-dielectric fused silica ceramic (FSC) substrate is compatible with digital light processing (DLP) technology owing to high molding precision and design flexibility. The current strategies such as increasing solid loading, raising sintering temperature or introducing second phases often failed to balance dielectric properties and mechanical strength of DLP printed FSC components. In this study, a wide particle size distribution strategy (WPSD, Span=4.360) was employed to optimize this problem. The viscosity of the 45 vol% WPSD ceramic slurry was reduced to 1.49 Pa·s and the high dimensional accuracy achieved precise tuning of the 3D FSS resonant frequency within a deviation of 0.14 GHz. Owing to the sintering activation effect of fine particles and the skeleton reinforcement effect of large particles, the WPSD fused silica ceramic demonstrated superior mechanical properties without any additives. It achieved a flexural strength of 28.2 MPa which surpassed most reported values for pure or doped DLP printed fused silica ceramics. Moreover, the printed WPSD ceramic exhibited a stable dielectric constant (2.21–2.28) and low dielectric loss tangent (0.55–1.28 ×10⁻³) over the frequency range of 8–40 GHz. Importantly, flexural strength and dielectric properties remained relatively stable after intense thermal shock test which demonstrated significant potential for applications in high-temperature wave-transparent components. This paper provides a new pathway to simultaneously achieve excellent dielectric properties and high mechanical performance in DLP printed fused silica ceramics which could be used for as next-generation FSS radomes.