Fabrication and Characterization of In Situ Porous S i 3 N 4 ‐ S i 2 N 2 O ‐ BN Ceramic

Porous S i 3 N 4 ‐ S i 2 N 2 O ‐ BN ceramic was fabricated at 1750°C using S i 3 N 4 , BN , and ( NH 4 ) 2 HPO 4 as starting materials. During the sintering process, oxygen from the decomposed products of ( NH 4 ) 2 HPO 4 would bond Si and N in the liquid phase to form S i 2 N 2 O . The microstructure and properties of the porous ceramics were investigated. With the ( NH 4 ) 2 HPO 4 content varied from 10 to 50 vol.%, porosity of the porous S i 3 N 4 ‐ S i 2 N 2 O ‐ BN ceramic increased from 43.5% to 51%. The microstructure, mechanical, and dielectric properties was well controlled by adjusting ( NH 4 ) 2 HPO 4 contents. The present technique offers a more simple way of synthesizing porous S i 3 N 4 ‐ S i 2 N 2 O ‐ BN ceramics.