Fabrication and characterization of in Situ Porous Si₃N₄-Si₂N₂^O-BN ceramic

Porous Si₃N₄-Si₂N₂^O-BN ceramic was fabricated at 1750°C using Si₃N₄, BN, and (NH₄)₂HPO₄ as starting materials. During the sintering process, oxygen from the decomposed products of (NH₄)₂HPO₄ would bond Si and N in the liquid phase to form Si₂N₂^Ox. The microstructure and properties of the porous ceramics were investigated. With the (NH₄)₂HPO₄ content varied from 10 to 50 vol.%, porosity of the porous Si₃N₄-Si₂N₂^O-BN ceramic increased from 43.5% to 51%. The microstructure, mechanical, and dielectric properties was well controlled by adjusting (NH₄)₂HPO₄ contents. The present technique offers a more simple way of synthesizing porous Si₃N₄-Si₂N₂^O-BN ceramics.