BN Nanoparticles/Si 3 N 4 Wave-Transparent Composites with High Strength and Low Dielectric Constant

Si 3 N 4 wave-transparent composites with different volume content of BN nanoparticles (BN np /Si 3 N 4 ) were prepared by gas pressure sintering at 1800°C in N 2 atmosphere. The effects of BN nanoparticles on the dielectric and mechanical properties of BN np /Si 3 N 4 composites were investigated. The results showed that the addition of the BN nanoparticles improved the dielectric properties of BN np /Si 3 N 4 composites effectively and decreased the mechanical properties. When the volume content of BN nanoparticles was 10%, the dielectric constant and dielectric loss tangent were 4.31 and 0.006, respectively, and the bending strength and fracture toughness still reached 198.9 MPa and 3.36 MPa·m 1/2 . The high mechanical properties of BN np /Si 3 N 4 composites with 10% BN nanoparticles were attributed to homogeneously dispersed BN nanoparticles which were embedded in the pores formed by the rod-like β -Si 3 N 4 .