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

Abstract

Si3N4 ceramics with improved and tailorable dielectric constant are desirable for microwave dielectric substrate application in harsh environment. Effect of BaTiO3 addition on the mechanical and dielectric properties of the hot-pressed Si3N4 ceramics with Al2O3 and Nd2O3 as sintering additives were investigated. Relative density, flexural strength and Vickers' hardness of Si3N4 ceramics all decreased, while indentation fracture toughness increased monotonically with the increase of BaTiO3 content. Flexural strength of Si3N4 ceramics was higher than 600 MPa and dielectric constant of Si3N4 ceramics increased to 9.26-11.50 when 5wt%-20wt% of BaTiO3 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 BaTiO3 was not detected in the sintered samples. These findings can make a significant contribution to the new applications of Si3N4 ceramics.