Mechanical and dielectric properties of gelcasted Si3N4 porous ceramic using CaHPO4 as an additive

Abstract The phase composition, relative density, mechanical properties and dielectric properties of silicon nitride porous ceramics with different content of CaHPO 4 as an additive prepared by gelcasting method were investigated. The addition of CaHPO 4 can improve the sintering ability and the phase transformation from α-Si 3 N 4 to β-Si 3 N 4 , so the relative density and β-Si 3 N 4 content both increase with the increase of CaHPO 4 content. As a result, when the CaHPO 4 addition content is 15 wt.%, the flexural strength, elastic modulus, fracture toughness of Si 3 N 4 ceramic reach to 365.1 MPa, 107.9 GPa and 3.82 MPa m 1/2 , respectively. The dielectric constant of Si 3 N 4 ceramics increases with the increase of CaHPO 4 addition content due to the increase of relative density and the relative content of β-Si 3 N 4 .