Revisiting the percolation phenomena in dielectric composites with conducting fillers

The composition (φ) dependence of the effective dielectric constant (ε_eff) on conductor-dielectric composites is widely described as εeff(φc-φ)-s. This relationship has been extensively used to fit experimental results for determining the percolation behavior (percolation threshold φ_c and power constant s). The equation was checked using experimental results from two 0-3 nanocomposite systems with uniform microstructures. It is found that the equation can be used to fit the experimental results, but the fitting constants (φ_c and s) do not reflect the percolation behavior: the values of both fitting constants are dependent on the frequency (f) and temperature selected. It is also found that the fitting constant φ_c increases with increasing frequency selected and it is believed that this arises from the critical phenomenon, εefffγ-1, for composites close to the φ_c.