Effect Of Nano-BaTiO₃ Surface Modification On Dielectric Properties Of PVDF Composites

With the rapid development of the electronics industry,especially in the field of high energy density,the comprehensive performance of flexible high-dielectric materials are put forward higher requirements.Therefore,the researches of inorganic/polymer matrix composites have attracted worldwide interests.The high doping concentration of inorganic particles can significantly improve the relative permittivity of the composites,but at the same time it will lead to a series of problems such as the agglomeration of inorganic particles,increasing the dielectric loss,decreasing the flexibility and reducing the breakdown performance of materials.And the disadvantageous will limit the practical application of inorganic/polymer matrix composites.In this paper,the BaTiO₃/PVDF composites were chose as the research object through the surface modification of BaTiO₃ inorganic nanoparticles.The effect of the deposition and coating of Cu onto the surface of BaTiO₃ inorganic nanoparticles on the dispersion,dielectric,loss and energy storage properties of composites was investigated.In order to improve the relative permittivity of the composites and suppress dielectric loss increasing,BaTiO₃ nanoparticles were modified by the metal nano-Cu to combine the advantages of conductive metal and BaTiO₃ inorganic nanoparticles.The two nano-microspheres of Cu-BaTiO₃ and Cu@BaTiO₃ were prepared by controlling the growth parameters of Cu nano-crystals via the chemical reduction method.The BaTiO₃,Cu-BaTiO₃ and Cu@BaTiO₃ nanoparticles were used as fillers to modify the PVDF matrix,and the dielectric and energy storage properties of the composites were investigated.The results show that the BaTiO₃ nanoparticles modified by Cu can obviously improve the relative permittivity of the composites,and the modification of Cu has a significant effect on the dielectric properties of the composites.The relative permittivity of the composites increases with the doping concentration increased.When the doping volume fraction is 20 vol%,the relative permittivity of Cu-BaTiO₃/PVDF and Cu@BaTiO₃/PVDF composite films are 101.3and 104.2 at 100 Hz,which are 12 and 12.5 times higher than the pure PVDF dielectric constant??r = 8.4?,and the dielectric loss was 0.09 and 0.14,respectively.Compared with Cu@BaTiO₃,Cu-BaTiO₃ can not only disperse the Cu nanoparticles in the PVDF matrix and improve the relative permittivity of the composites,but also hinder the formation of the conductive channels to suppress the rapid increasing conductivity and dielectric loss.In addition,the high doping concentration of inorganic nanoparticles led to the decrease of the mechanical flexibility and the breakdown electric field of the composites.The surface-modified BaTiO₃ by Cu nanoparticles could achieve higher relative permittivity at lower doping concentration and maintain the flexibility and higher breakdown field strength of the materials,which is beneficial to the practical application of polymer-based nano-composites.