Microstructure and dielectric characterization of micro- nanosize co-filled composite films with high dielectric permittivity

Dielectric composite films of the micro-nanosize BaTiO₃ (BT) particles embedded into a polyvinylidene fluoride (PVDF) matrix were prepared by using a simple blending and casting processing. Effects of the micro-nanosize cofilled model at different mciro-nanosize volume ratios of BT particles on microstructure and dielectric properties of the composite films were researched. The results show that the nanosize BT particles can be filled into the gaps between the micron-size BT particles so that a tightly stack structure in the BT/PVDF composite film is formed. As a result, the dielectric properties of the composite films with the micro-nanosize BT loading at 40 vol% is higher than these with single nanosize BT loading solely if the interactions between the BT fillers are considered. The maximum values of dielectric permittivity were about 55 because of the superior internal microstructure of composite films when the mciro-nanosize volume ratio of BT particles is close to 1/1. In this case, a remarkable synergistic effect for improving the dielectric properties was also observed. The microstructure and the assumed cofilled model of the composite films would used to explain the experimental results well.