A comparative study on dielectric and mechanical properties of porous β-Si3N4 ceramics by controlling porosity and microstructure

To ensure the porous Si3N4 ceramics with an excellent comprehensive performance for the application of radome, the commonly neglected effect of designed microstructures on dielectric and mechanical properties was investigated. Two typical porous Si3N4 ceramics with similar porosity but different microstructures (unidirectionally aligned and uniformly micropore structure with a different dimension of grains) were obtained by freeze casting and gel-casing process. The results indicate that the microstructure has a significant influence on the mechanical properties yet not an obvious effect on the dielectric properties, which means the dielectric constant can be reliably designed based on the porosity without consideration of different microstructures, meanwhile, the mechanical properties can be optimized by the microstructure. Besides, the results of the dielectric properties predicted by Finite Element Analysis show a high agreement with the experimental results. The study could be helpful to design a wave-transmitting component with integrated structure and function.