Investigation On High Dielectric Properties Of Magnetic Nanoparticles/Polymer Composites

Recently, high-performance capacitors call for the smaller size and multi-function. And theflexible composites with a high dielectric constant have gained the great attention in the future forthe electron and electric industry. The Fe₃O₄nanoparticle has been widely used as multifunctionalmaterials in magnetofluid, sensors, and biological medicine, etc. It is well known that Fe₃O₄hasexcellent electrical performance, which can be used as the conductive filler in the dielectriccomposites.In this paper, the Fe₃O₄particles were prepared by hydro-thermal method. Then the surface ofFe₃O₄was treated with oleic acid. The structure, morphology and magnetism of the compositeparticles were characterized by X-ray diffraction（XRD）, Fourier transform infraredspectroscopy（FT-IR）, transmission electron microscope（TEM） and scanning electronmicroscopy（SEM）. It was confirmed that the magnetic particles was pure Fe₃O₄nanoparticle. TheFT-IR spectra of the coated Fe₃O₄nanoparticles showed that the chelating bidentate interactionbetween the–COOH group of oleic acid and the iron ions was formed, and the coated Fe₃O₄nanoparticles were uniform spherical and had good dispersion.Here the Fe₃O₄nanoparticles and the oleic acid coated Fe₃O₄nanoparticles have been chosenas the candidate fillers in the polyvinylidene fluoride （PVDF） polymer matrix, which is anexcellent ferroelectric polymer. Phase structures and morphologies of the composite werecharacterized by scanning electron microscopy（SEM）, and the dielectric properties of sampleswere mearsured using Agilent4294A precision impedance analyzer. A distinct percolation effecthas been found in Fe₃O₄/PVDF composites, companying with high dielectric constant （5240at100Hz）, low-loss （2.2at100Hz） and good superparamagnetic performance. So the composite isexpected to be used in magnetoelectricity materials. The percolation effect of the modified Fe₃O₄/PVDF composite occurred when the weight fraction of particles was increased to37.5%, and themicrostructure of the composite material is vortex structure. Besides, the influence of themicrostructure on the dielectric properties needs further study.