Nonlinear dielectric response of periodic composite materials

This paper addresses the rigorous treatment of the tunability effect (dc electric field driven variation of the permittivity) in a high-contrast two dimensional periodic composite (a matrix of a large dielectric constant ferroelectric material with linear dielectric inclusions). The theoretical analysis here shows that the trend established for the case of low linear dielectric concentrations (that the dilution with a low permittivity dielectric does not result in decrease of the tunability of the composite material), can hold for appreciable dielectric concentrations. We have even documented a pronounced increase of the tunability. The results of our simulations are in qualitative agreement with the experimental data on the composite effect in ferroelectric/dielectric binary-phase systems. The result of the numerical analysis gives no support to the "decoupled approximation" in the effective medium approach often used for the description of the dielectric non-linearity of composites.