Dielectric Performance And Energy Storage Behavior Of BaTiO₃-Cu/PVDF Composites With Core-satellite Structure Fillers

Polymer based nanocomposites with high permittivity offer the promise of flexible, scalable and low-cost devices, and have attracted much interest in energy storage, electronic and electrical applications. Meanwhile, with the development of high-frequency communication in cellular, radio navigation, base station and collision avoidance system, composites with high dielectric performance up to gigahertz(GHz) are highly desired, which however, have been rarely investigated.In the polymer based composites, it has been deemed that interfacial polarization plays the primary mechanism for the enhanced dielectric permittivity and never could be neglected. In a composite system with poor dispersion of the inorganic fillers, however, high permittivity can only be obtained at low frequency(e.g.<1 k Hz) accompanied with an interfacial relaxation, which is caused by the accumulated free charges in the hetero system. It's of great importance to guarantee the interfacial polarization at much higher frequency even at GHz.On the other hand, the pursuit of high-k make us overlook the dielectric loss, in most cases, high-k materials can be reach with the sacrifice of dielectric loss. So, it is also very important to suppress the loss tangent at the same time when the permittivity got improved.Meanwhile, the energy storage behavior of dielectric composites should be deeper as the enormous demand for energy storage equipment.In this work, a strategy was proposed to combine the advantages of ceramic, conductor and polymer matrix to obtain the three-phase composites with prominently enhanced dielectric properties, in which nano Cu was deposited on the surface of Ba Ti O3 grains to form BT-Cu hybrids and used as fillers.Hybrid ceramic-metal particles were synthesized through a simple hydrothermal method, and the as-synthesized BT-Cu were subsequently coated with polyethylene glycol 4000(PEG-4000). In the obtained BT-Cu hybrids, the Cu nanoparticles are discretely grown and bond tightly to the BT grains. As a result, homogeneous dispersion of both BT and Cu particles are guaranteed when the hybrids are used as fillers to prepare the polymeric composites. The permittivity value at the Gigahertz is almost the highest one ever reported for the polymer composites. A systematic analysis on the antioxygenic property of BT-Cu, dielectric performance, the energy storage characteristics and polarization mechanism of the BT-Cu/PVDF composites were investigated based on Maxwell-Wagner polarization theory, effective medium theory percolation(EMPT) model and analysis on electric modulus.