Toward improved PVDF-BaTiO3 composite dielectrics: mechanical activation of the filler versus filler content

Abstract

Barium titanate (BT) perovskite particles were surface modified by means of mechanical treatment and used as inorganic component in polyvinylidene fluoride (PVDF) based composites. The changes in electrical properties of the composite films with increasing in filler content were followed by dielectric spectroscopy, breakdown strength and D-E measurements. A comparison of the properties of the composites prepared with untreated and mechanically activated particles revealed that there is a significant difference in their performances at low filler concentrations (<20 wt%). Introduction of the surface modified ceramic particles into PVDF matrix led to an increase of the dielectric constant without affecting significantly the electrical breakdown strength. In contrast, when as received BT particles were used a filler, both dielectric constants and breakdown strengths of the composite films were lower than the corresponding values observed for the pure PVDF. At higher concentrations, however, the influence of pre-treatment of the filler on the effective electrical properties becomes less significant. The obtained results were discussed in terms of the pronounced crystallization of polar β and γ crystal phases of PVDF in the presence of surface modified BT fillers, which is confirmed by Raman spectroscopy.