Preparation And Properties Of Poly?Vinylidene Fluoride?/Nd-doped BaTiO₃ Nanocomposites

In order to obtain the ceramic-polymer nanocomposite with high breakdown strength,high dielectric properties,low loss,high energy storage density and good flexibility,Nd-BaTiO₃ nanoparticles with high dielectric constant were used to prepare Nd-BaTiO₃ / PVDF nanocomposite for the first time.The nanoparticles were then modified by dopamine,and their effects on the microstructure,phase structure,dielectric and energy storage properties of the nanocomposite were studied.It is found that the Nd-BaTiO₃ nanoparticles hardly affect the phase structure of the composite films.The dielectric constant of the nanocomposite increases with the increase of Nd-BaTiO₃ content.The interface compatibility between Nd-BaTiO₃ and PVDF is so poor that the breakdown strength of the nanocomposite is badly reduced.The breakdown strength of PVDF-1 vol% Nd-BaTiO₃ is 360 MV/m and the discharged energy density reaches the maximum value of 7.9 J/cm3,while the discharged efficiency is only 38 %.The dopamine modification enhances the interfacial compatibility between nanoparticles and PVDF,as well as the dispersion of nanoparticles in PVDF.And the breakdown strength of the nanocomposite is hence improved.Under the same condition,the dielectric constant and loss of PVDF-dopamine@Nd-BaTiO₃ are higher than those of PVDF-dopamine@BaTiO₃.In addition,the higher dielectric constant of the Nd-BaTiO₃ gives rise to serious electric field distortion at the interface.As a result,the breakdown strength of PVDF-dopamine@Nd-BaTiO₃ is less than PVDF-dopamine@BaTiO₃.Meanwhile,the higher dielectric constant leads to the higher interfacial polarization.Under the electric field of 420 MV/m,the discharged energy density of PVDF-1 vol%dopamine@Nd-BaTiO₃ reaches the maximum value of 12.5 J/cm3,and the discharged efficiency is as high as 48 %.With the increase in the annealing temperature,the micromorphology of Nd-BaTiO₃ changes from initial spherical to tetragonal particle,and the phase structure changes gradually to tetragonal phase.The dielectric constant and loss of the nanocomposite have both increased with the increasing annealing temperature.Under the electric field of 380 MV/m,the sample of PVDF-1 vol%dopamine@Nd-BaTiO₃-800°C achieves the largest discharged energy density of 10.4 J/cm3,and the discharged efficiency is as high as 49 %.