Piezoelectric and Dielectric Response of BaTiO₃/PVDF-TrFE Composites with High β‑Phase Content

The search for flexible piezoelectric materials to build adaptable sensors, electronics, and nanogenerators has become a key area of interest. The addition of piezoceramic particles to piezoelectric polymers, such as the copolymer poly-(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE), is one of the strategies used to enhance the piezoelectric response. In this work, the effect of BaTiO₃ content on the β-phase formation, crystallization, and piezoelectric and dielectric properties of the polymer-based composites is investigated. High-energy ball milling was used as an effective, greener technique to achieve well-dispersed mixtures compared to those obtained using organic solvents. During the dispersion process, amorphization and reduction of the crystalline domain size occur. After compression molding and postprocessing, the crystallinity was recovered and was strongly dependent on the filler content. Although significant differences in the β-phase fraction were not observed, conformational defects are induced with high BaTiO₃ contents. The interlayer distances became smaller due to the presence of the ceramic particles after compression molding and remained almost unchanged after postprocessing. For the composites, the minimum voltage required to obtain a measurable piezoelectric coefficient (d ₃₃ ) was significantly reduced compared to neat PVDF-TrFE, even for low contents, which is key for real applications. Three different piezoelectric behaviors were found depending on the BaTiO₃ fraction. For composites with 40 vol %, where both matrix and filler contribute to the overall piezoelectric response, the use of a two-step poling method induced a synergistic effect with an increase in d ₃₃ of ∼180%. However, the relaxation of the ceramic contribution after 24 h returns the value of d ₃₃ to that obtained by applying a one-step poling strategy.