Effect of BN content on the mechanical and dielectric properties of porous BNp/Si3N4 ceramics

Porous BNp/Si3N4 ceramics were prepared by gas pressure sintering method as a candidate wave-transparent material. The effects of BN particle additions ranging from 0 wt% to 15 wt% on the phase compositions, microstructures, mechanical performance and dielectric properties were investigated. With the increase of BN content, the apparent porosity of the BN/Si3N4 ceramics increased greatly from 2.3% to 21.2%. Although the mechanical properties were partially weaken, the dielectric performance of the porous BN/Si3N4 was largely enhanced at the same time. For the 10% BN/Si3N4 porous composite ceramics, the permittivity and dielectric loss was 33.5% and 62.2% lower than that of the porous Si3N4 without BN content, respectively. Specifically, when 10% BN particles were added, the porous BNp/Si3N4 has a porosity of 20.5% and the permittivity and dielectric loss were 5.14 and 0.0085 respectively with bending strength of 190.1 MPa and fracture toughness of 4.16 MPa m1/2, which can meet the required value of wave transparent materials.