PVDF - BaTiO3 composites as dielectric materials for efficient energy storage

In this work polymer-based composites containing 10-35 vol.% BaTiO3 nanoparticles were prepared by melt blending followed by compression moulding to obtain sheets 0.5-1 mm thick. A commercial poly(vinylidene fluoride) (PVDF, SOLEF 1008 Solvay) grade was chosen as polymer matrix and BaTiO3 particles (diameter ca. 100 nm) synthesized by a hydrothermal-like method [3] were used as inorganic inclusions. The BaTiO3 particles were used bare or surface-modified with proper coupling molecules (silane derivatives) [4] and/or coated with a thin TiO2 shell (thickness 5-20 nm). Such engineered polymer/ceramic interfaces should facilitate the fine dispersion of the inclusions leading to a more homogeneous distribution of the electric field. Microstructural features and thermal behaviour of the ensuing composites were characterized by SEM, TG and DSC analyses. The amount of the ferroelectric crystalline ? phase in the PVDF matrix was determined by FT-IR spectroscopy and X-ray diffraction. The dielectric constant and the loss tangent of the composite materials were measured at different frequencies by impedance spectroscopy. Simulation of the field distribution in model composites was performed by 3D finite element modelling and correlated with the experimental evidences.