Preparation and dielectric property of MWCNT/CCTO/PVDF composite film

By employing poly(vinylidene fluoride) (PVDF) as matrix material, CaCu₃Ti₄O₁₂ (CCTO) as ceramic filler, and multi-walled carbon nanotube (MWCNT) as conductive material, MWCNT/CCTO/PVDF three-phase composites were fabricated through a solution blending-casting method. Micro morphology (by Scanning electron microscope, SEM), crystalline structure (by X-ray diffraction, XRD) and the dielectric properties of the materials were analyzed. SEM images show that the addition of MWCNT in composite materials promote CCTO well dispersed in the PVDF matrix. Nevertheless, excessive MWCNT will degrade the performance of materials. Dielectric property test results show that at room temperature and 100 Hz, when 30 vol% CCTO powder was used, CCTO/PVDF composite showed the optimal dielectric properties with dielectric constant 16.5 and dielectric loss 0.075, but there were still many holes and obvious flaw in the material. When 4.0 vol% MWCNT was added into above composite, the dielectric constant and loss of the three-phase composite were 55.733 and 0.251 respectively. Compared with CCTO/PVDF composite (0.617 J • cm^-3), the energy storage density of MWCNT/CCTO/PVDF composite (1.395 J • cm^-3) increased. The research shows that when the MWCNT content reaches the percolation threshold, the dielectric constant of composite materials increase dramatically and good comprehensive performance could be obtained.