The aim of this research is the development of low loss ferroelectric material for microwave applications. Ferroeletric materials are nonlinear dielectrics having a dielectric constant which is a function of the electric filed. The nonlinear behavior of these materials makes them good candidates for the realization of advanced high frequency devices such as phase shifters.

Ferroelectric materials (FEM) are very attractive because their dielectric constant can be modulated under the effect of an externally applied electric field perpendicular to the direction of propagation of a microwave signal. FEM may be particularly useful for the development of a new family of planar phase shifters which operate up to X-band. The use of FEM in the microwave frequency range has been limited in the past due to the high losses of these materials and due to the high electric field necessary to bias the structure in order to obtain substantial dielectric constant change. We demonstrate in our research how a significant reduction in material losses is possible. We achieve this by using a new sol-gel technique.

The use of ferroelectric materials in ceramic form for the realization of a phase shifter operating at 2.4 GHz was recently demonstrated in our group. The phase-shift capability of FEM results from the fact that if we are below the Curie temperature, the dielectric constant of such a material can be modulated under the effect of an electric bias field. Particularly, if the electric field is applied perpendicularly to the direction of propagation of the electromagnetic signal, the propagation constant of the signal will depend upon the bias field. The total wave delay will become a function of the bias field, and therefore this will produce a phase shift.