The effect of BaTiO3 addition on the dielectric constant of Si3N4 ceramics

Si3N4 ceramics with different BaTiO3 contents have been fabricated by pressureless sintering in a N-2 atmosphere at 1680 degrees C for 2 h. Al2O3 and Nd2O3 were used as sintering additives to promote the densification of Si3N4 ceramics. The effect of BaTiO3 addition on the densification, mechanical properties, phase compositions, microstructure, and dielectric properties of Si3N4 ceramics was investigated. The relative density and flexural strength of Si3N4 ceramics increased with the addition of BaTiO3 up to 15 wt% and then decreased, while the dielectric constant increased continuously as the BaTiO3 contents increased. The dielectric constant of Si3N4 ceramics can be tailored in the range from 8.42 to 12.96 by the addition of 5 wt%-20 wt% BaTiO3. Meanwhile, these Si3N4 ceramics all had flexural strength higher than 500 MPa.