Enhanced tunability in ferroelectric composites through local field enhancement and the effect of disorder.

We investigate numerically the homogenized permittivities of composites made of low-index dielectric inclusions in a ferroelectric matrix under a static electric field. A refined model is used to take into account the coupling between the electrostatic problem and the electric field dependent permittivity of the ferroelectric material, leading to a local field enhancement and permittivity change in the ferroelectric. Periodic and pseudorandom structures in two dimensions are investigated, and we compute the effective permittivity, losses, electrically induced anisotropy, and tunability of these metamaterials. We show that the tunability of such composites might be substantially enhanced in the periodic case, whereas introducing disorder in the microstructure weakens the effect of the enhanced local permittivity change. Our results may be useful to guide the synthesis of novel composite ceramics with improved characteristics for controllable microwave devices. [ABSTRACT FROM AUTHOR]