High-frequency magnetic and dielectric properties of a three-phase composite of nickel, $Co2Z$ ferrite, and polymer

A three-phase, double-percolating composite with $Co2Z$ ferrite particles and nickel particles embedded in a poly(vinylidene fluoride) matrix was prepared by using a simple low-temperature hot-pressing technique. The large ferrite particles in the composite not only act as the magnetic phase but also present as a high volume fraction discrete (nonpercolating) phase, confining polymer and metallic particles into a continuous double-percolating structure of low volume fraction. With the addition of a small number of magnetic nickel particles, a large enhancement in both initial permeability and dielectric constant of the three-phase composite was observed. This can be explained by effective medium approach and percolation theory. The three-phase composite showed both frequency-independent inductive and capacitive properties in the high-frequency range up to $∼500MHz$⁠. Such a multifunctional magnetic-electric three-phase composite could be used in high-frequency communications and electromagnetic interference filters not only as an inductor but also as a capacitor.