PVDF-BaTiO3 composite dielectrics: influence of processing and particles modification on properties

Polymer-based composites are very attractive for advanced applications in the field of energy harvesting, storage and conversion. For instance, the introduction of high-permittivity ceramic particles into a polymer matrix, characterized by high breakdown field, leads to dielectric materials able to store large amounts of energy while maintaining desirable properties of the polymer, such as processability and flexibility. In particular, poly(vinylidene fluoride) (PVDF) is widely used as matrix due to its higher dielectric permittivity (?10), compared to other polymers, and its capability to crystallize in five different polymorphs, some of which possess a neat moment dipole. In this work 0-3 connectivity PVDF-based composites containing 30 vol% ferroelectric BaTiO3 (BT) ceramic inclusions were prepared by solution casting followed by compression molding, properly adjusting the processing conditions in order to induce the formation of the electro-active ? polymorph of PVDF. Three different compression molding methods were employed for realizing PVDF-BaTiO3 composites: the most promising procedure was then used for the preparation of composites containing modified, i.e. core-shell and/or functionalized, BT nanoparticles. All nanoparticles were characterized by FTIR and TEM. A thorough characterization was performed on the composites to investigate the influence of processing conditions and of filler type on the resulting dielectric properties, taking into account PVDF polymorphism and particles dispersion within the polymer matrix.