Tunability of Granular Ferroelectric Dielectric Composites

Abstract

Abstract-Electrical tunability of a composite consisting of small ferroelectric spheres randomly dispersed into a dielectric background is studied. A new method to calculate the effective permittivity of such a nonlinear composite is introduced. The method is based on the Bruggeman effective medium theory and a specific model for the nonlinear permittivity of the ferrite. The resulting tunability (defined as a measure of the change in the permittivity due to the bias field) is a continuous function of the volume fraction of the ferroelectric material phase in the composite. As an example, SrTiO 3 is studied with two different nontunable background materials.

Microwave Tunable Metasurfaces Implemented With Ferroelectric Materials and Periodical Copper Wires

“…SrTiO 3 is a commonly used ferroelectric at microwave frequencies [20,22,23]. In this work, the parameters of SrTiO 3 are chosen to be T C = 42 K, Θ F = 175 K, ξ S = 0.018, 00 = 2081, E N = 19.3 kV/cm, α = 2 × 10 9 m −1 [20].…”

“…Figure 1 shows the structure of a three-layered metasurface, satisfying the plasmonic resonant condition, p = − f , where p and f are the permittivity of the plasmonic material and the ferroelectric, respectively. The permittivity of the latter can be tuned by applying a bias voltage up to several hundreds even thousands of volts, at frequency up to 100 GHz [20].…”

“…Electromagnetic tunability for different applications has been implemented with electro-optic crystal [18], liquid crystal [19], and ferroelectric materials [20]. However, fewer discussions have been given to the tunability of metasurfaces.…”

Homogenized Permittivity of Composites With Aligned Cylindrical Inclusions for Causal Electromagnetic Simulations

“…Therefore, (6) provides not a single real value, but a complex and frequency-dependent relaxation time. However, the imaginary part has been found to be much smaller than the real part for all the cases investigated (Im[τ Dx,y,z (ω)] ≈ 10 −6 ·Re[τ Dx,y,z (ω)]), and it can be simply neglected.…”

“…These materials allow for high design flexibility, since they can be adapted to achieve complex shapes and ad-hoc strength levels, provide sound and heat isolations, as well as good electromagnetic shielding protection [3][4][5][6][7]. Micro/nano fabrication processes, indeed, allow for making composites of carbon nanotubes, which could be used in various devices, e.g., actuators [8][9][10][11][12].…”