A systematic study on electrical properties of the BaTiO3-epoxy composite with different sized BaTiO3 as fillers

The epoxy composites consisting of BaTiO3 fillers with size of 100 nm and 200 nm were prepared, respectively. The thermo-mechanical and electrical properties of BaTiO3-epoxy composites were investigated using complex permittivity, electric modulus and ac electrical conductivity. The effects of filler size on the structure, filler-matrix interface and properties were discussed. The Havriliak-Negami model was used to analyze the dielectric relaxation of composites. The results show that larger filler tends to exhibit enhanced dynamic modulus and higher Tg because of the increase of effective volume fraction. The tetragonal phase formation in the BaTiO3 is important to achieve enhanced permittivity of the composite. The relaxation responses of composites revealed by electric modulus and complex permittivity show that the Maxwell-Wagner-Sillars (MWS) polarization and tetragonal phase transition of BaTiO3 affect the dielectric responses of composites. The conduction process is not only related with the barrier hopping but also tunneling effect of electrons. Based on the electrical properties of BaTiO3-epoxy composite with 100 nm BaTiO3 at GHz, a compact band-pass filter with significant area reduction was designed and fabricated. The measured results show that the BaTiO3-epoxy composite is promising for advanced wireless device applications.