Preparation and Properties of Si_3N_4-BaTiO_3 Composite Ceramics

摘要

Si_3N_4-BaTiO_3 composite ceramics, a type of high dielectric materials applied in the multifunction radome, were prepared by gas pressure-sintering method. The influences of BaTiO_3 power content on the mechanical performances, dielectric properties and microstructure of Si_3N_4-BaTiO_3 composite ceramics were investigated. The results showed that the sintering density, the elastic modulus and the flexural strength of Si_3N_4-BaTiO_3 composite ceramics all firstly increased and then decreased along with the increase of BaTiO_3 power in sample. Meanwhile, Relationship between BaTiO_3 power content and dielectric properties of Si_3N_4-BaTiO_3 composite ceramics within the frequency range of 8.2-12.4 GHz (X-band) was studied. The average of dielectric constant ε of Si_3N_4-BaTiO_3 composite ceramics increased from 7.33 to 9.98 and the average of dielectric loss tanδ increased from 2.8 × 10~(-3) to 0.0168 when the content of BaTiO_3 power increased from 0 to 25 wt.%. The increase of the dielectric properties of Si_3N_4-BaTiO_3 composite ceramics were attributed to the electronic and molecular polarization at interface between Si_3N_4 and BaTiO_3, compared with the pure matrix Si_3N_4.