Abstract
In this paper, we report the dielectric properties of composite systems (nanodielectrics) made of small amounts of mono dispersed magnetic nanoparticles embedded in a polymer matrix. It is observed from the transmission electron microscope images that the matrix polymeric material is confined in approximately $100\ \nano\meter$ size cages between particle clusters. The particle clusters are composed of separated spherical particles which constructed unconnected networks in the clusters. The dielectric relaxation and breakdown characteristics of the matrix polymeric material are altered with the addition of nanometer size cobalt iron-oxide particles. The dielectric breakdown measurements performed at $77\,\kelvin$ showed that these nanodielectrics can be utilized as an electrical insulation material for cryogenic high voltage applications instead of the unfilled poly(methyl methacrylate). Finally, structural and dielectric properties of nanocomposite dielectrics are discussed to present plausible reasons for the observed low effective dielectric permittivity values in the present and similar nanodielectric systems. It is concluded that polymeric nanoparticle composites would have low dielectric permittivity no matter what the permittivity of nanoparticles are when the particles are coordinated with a low dielectric permittivity surfactant.
