On the question of percolation threshold in polyvinylidene fluoride/nanocrystalline nickel composites

The dielectric behavior of polyvinylidene fluoride (PVDF), nanocrystalline nickel (nc-Ni) composites has been investigated over a broad frequency range of 40 Hz-10 MHz. High effective dielectric constant (epsilon(eff)=2050) and low loss (tan delta=10) at 100 Hz have been observed near the percolation threshold. To the best of our knowledge, this is the highest epsilon(eff) value reported to date among the PVDF based metal-polymer composites. The dielectric properties have been explained by using boundary layer capacitor effect and percolation theory while the dielectric anomalies are attributed to process of fabrication leading to thick insulating layer between the filler particles forming a gap in effective tunneling range of two filler particles and also making a difficulty in probability of higher order tunneling.