Model of a low-permittivity and high-tunability ferroelectric based composite

It is shown that a prominent feature of ferroelectric-dielectric composites-the possibility of reducing their permittivity while keeping their tunability-may be substantially enhanced when using a ferroelectric matrix with "flatten" dielectric inclusions (inclusions with one dimension much smaller than two others). The composite containing flat inclusions oriented normal to the applied electric field is expected to yield a dielectric performance similar to that of the composite with nonflatten inclusions, albeit at much smaller concentrations of the dielectric. This effect is demonstrated from small-signal dielectric nonlinearity in diluted composite with spheroidal dielectric inclusions. It is proposed to use the composites of the considered structure in microwave systems in which low-permittivity tunable materials are required. (C) 2007 American Institute of Physics.