Effect of chemical vapor deposition of Si3N4, BN and B4C coatings on the mechanical and dielectric properties of porous Si3N4 ceramic

The mechanical properties of porous Si3N4 ceramic are noticeably improved after chemical vapor deposition (CVD) of Si3N4, BN and B4C coatings. The dielectric constant and loss of porous Si3N4 ceramic remain almost unchanged after CVD of BN, increase slightly after CVD of Si3N4, but increase greatly after CVD of B4C. Overall, CVD of Si3N4 performs better than CVD of BN and B4C in improving the mechanical properties and keeping the low dielectric constant and loss of porous Si3N4 ceramic.