Magnetic and high-dielectric-constant nanoparticle polymer tri-composites for sensor applications

Multifunctional composites can be achieved by adding two different fillers with complementary properties to a polymer matrix. In this work, novel tri-composite multifunctional materials based on the incorporation of dielectric BaTiO3 (BT) and magnetic CoFe2O4 (CFO) nanoparticles into poly(vinylidene fluoride) (PVDF) have been developed with enhanced dielectric and magnetic responses for applications in areas such as energy harvesting, sensors and actuators. The microstructure, polymer phases as well as the thermal stability of the samples were investigated, showing the independence of the polymer crystallization phases, degree of crystallinity and melting temperature on filler type and contents. Further, independent of the type of the filler, its content improves the degradation temperature of the tri-composites. The magnetic properties and electrical conductivity of the tri-composites are correlated with the increase in the content of the CFO filler, while the dielectric response is mainly determined by the interfacial polarization. A high dielectric constant of 26 at 1 kHz and a magnetization of 5.7 emu * g−1 are obtained for a sample of 10 wt% CFO–10 wt% BT/PVDF, which was used for the demonstration of the suitability of the materials for magnetic deformation sensing. This work provides pathways for the development of tri-composites based on PVDF with high dielectric constant and magnetic properties for application in areas such as sensors and actuators.