Study on Polarization and Depolarization Characteristics of Epoxy/BaTiO 3 Nano-composites

Epoxy/BaTiO 3 Nano-composites with filler loadings of 0, 0.5, 1, 3 and 5 wt% are prepared. The polarization and depolarization relaxation currents of the composites are measured under different DC electric fields to explore the effects of the filler loading of BaTiO 3 on the properties of the composites. The samples are analyzed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. It is found that the BaTiO 3 particles are uniformly dispersed and the coupling agent played a role in linking BaTiO 3 particles with epoxy molecular chains. The experiment results show that the conductivity of the composites exhibits non-linear characteristics after the addition of BaTiO 3 into pure epoxy. When the BaTiO 3 filling loading is increased to 5 wt%, the conductivity of the composite material is significantly increased. And the $\mathbf{I}(\boldsymbol{t})\cdot \boldsymbol{t}-\mathbf{log}(\boldsymbol{t})$ curves calculated from depolarization currents of the samples with different filler loadings show that the time of peak value appears earlier with the increase of filler loading, which indicates that more shallow traps are introduced into the composites when increasing the filler loading based on isothermal relaxation current (IRC) theory.