Ferroelectric-dielectric tunable composites

Abstract

The dielectric response of ferroelectric-dielectric composites is theoretically addressed. Dielectric permittivity, tunability (relative change of the permittivity driven by dc electric field), and loss tangent are evaluated for various composite models. The analytical results for small dielectric concentration and relative tunability are obtained in terms of the traditional electrostatic consideration. The results for large tunability are obtained numerically. A method is proposed for the evaluation of the tunability and loss at large concentrations of the dielectric. The basic idea of the method is to reformulate the effective medium approach in terms of electrical energies stored and dissipated in the composite. The important practical conclusion of the paper is that, for random ferroelectric-dielectric composite, the addition of small amounts of a linear dielectric into the tunable ferroelectric results in an increase of the tunability of the mixture. The loss tangent of such composites is shown to be virtually unaffected by the addition of moderate amounts of the low-loss dielectric. The experimental data for (Ba,Sr)TiO3 based composites are analyzed in terms of the theory developed and shown to be in a reasonable agreement with the theoretical results.

Ferroelectric-Dielectric Solid Solution and Composites for Tunable Microwave Application

“…As Tagantsev stated (Tagantsev et al 2006), mixing a tunable ferroelectric with a linear dielectric may modify the electrical properties of the material due to mainly two effects: (i) "doping effect",-effect of doping of the ferroelectric lattice via the substitution of the ions of the host material and (ii) "composite effect"-effects of redistribution of the electric field in the material due to the precipitation of the non-ferroelectric phase at the grain boundaries or in the bulk of the material. The first effect results primarily in a shift and smearing of the temperature anomaly of the permittivity.…”

“…The overall tunability of the composite, thus changes. Two competitive phenomena affect the tunable properties of the ferroelectric when it is diluted with a dielectric (Sherman et al 2006). First, the reduction of the volume of ferroelectric, which is responsible for tuning, will cause suppression of the tunability of the material.…”

“…Some authors addressed the dielectric response of ferroelectric-dielectric composites theoretically and various composite models were used to evaluate the dielectric constant, tunability, and loss tangent Sherman et al 2006;Tagantsev et al 2006). As Tagantsev stated (Tagantsev et al 2006), mixing a tunable ferroelectric with a linear dielectric may modify the electrical properties of the material due to mainly two effects: (i) "doping effect",-effect of doping of the ferroelectric lattice via the substitution of the ions of the host material and (ii) "composite effect"-effects of redistribution of the electric field in the material due to the precipitation of the non-ferroelectric phase at the grain boundaries or in the bulk of the material.…”

Modeling of the evolution of dielectric loss with processing temperature in ferroelectric and dielectric thin oxide films

“…The spherical inclusion model is schematically illustrated in figure 1. It is proposed that a modified effective medium approximation (MEMA) approach could be applied to describe the dielectric responses of ferroelectric-dielectric composites [12]. Accordingly, the effective loss tangent of the composite can be given by …”

Near-field scanning optical microscopy to study nanometric structural details of LiNbO3 Zn-diffused channel waveguides

“…It is based on the effective medium theory, which recently has been successfully applied to ferroelectric materials. 22 The effective dielectric constant eff ͑and therefore the refractive index͒ for a D-dimensional composite ͑in our case we limit the model to D =2͒ comprising nanocrystals with permittivity nano and a filling factor p with respect to the host medium ͑the upper layer͒ with a permittivity up is given by As a difference, we just consider the area corresponding to the light cone cross section limited by the detector and, consequently, the filling factor is determined with respect to such area, as indicated in Fig. 2͑c͒ ͑i.e., the isosceles triangle determined by ␤ c ͒.…”