Mechanical and Dielectric Properties of Hot-pressed Si3N4 Ceramics with BaTiO3 Addition

Si 3 N 4 ceramics with improved and tailorable dielectric constant are desirable for microwave dielectric substrate application in harsh environment.Effect of BaTiO 3 addition on the mechanical and dielectric properties of the hot-pressed Si 3 N 4 ceramics with Al 2 O 3 and Nd 2 O 3 as sintering additives were investigated.Relative density, flexural strength and Vickers' hardness of Si 3 N 4 ceramics all decreased, while indentation fracture toughness increased monotonically with the increase of BaTiO 3 content.Flexural strength of Si 3 N 4 ceramics was higher than 600 MPa and dielectric constant of Si 3 N 4 ceramics increased to 9.26-11.50when 5wt%-20wt% of BaTiO 3 was added.The dielectric loss was at the level of 10 -3 .The improvement of dielectric constant was attributed to the formation of TiN during hot pressing, as crystalline BaTiO 3 was not detected in the sintered samples.These findings can make a significant contribution to the new applications of Si 3 N 4 ceramics.