Modeling the Permittivity of Ferrite-Dielectric Composites

Abstract

The paper presents the model of ferrite-dielectric (ferroelectric) composites with semiconductive powder fillers. Such media have the potential for designing systems with controlled frequency dispersion. Experimentally observed significant increase of effective dielectric permittivity in Mn-Zn ferrite composites with the semiconductor pellet is explained on the basis of the capacitance effect. Composites based on Ni-Zn ferrite, which have significantly higher electrical resistance, do not exhibit such phenomena and their behavior is described in the framework of the traditional models of effective medium approximation. There is proposed an analytical solution for the dielectric constant of the composite, based on consideration of the impedances of equivalent circuit involving initial materials (matrix and filler).

Electromagnetic properties of polymer composites Li-=SUB=-0.33-=/SUB=-Fe-=SUB=-2.29-=/SUB=-Zn-=SUB=-0.21-=/SUB=-Mn-=SUB=-0.17-=/SUB=-O-=SUB=-4-=/SUB=-/P(VDF-TFE) in the frequency range 100-7000 MHz

“…Figure 3 shows the spectra of the real part of dielectric permittivity. With increases of ferrite concentration the ε ′ of the composites also increase, that correlates with theoretical models of effective medium, in which the effective dielectric permeability of heterogeneous medium is a function of permeabilities of individual components [25]. Such statement is correct, since, as shown in the figure, dielectric permeability of F2M polymer is ∼ 3.5, and of Li-Mn-Zn ferrite is ∼ 6.…”

Radio-Absorbing Magnetic Polymer Composites Based on Spinel Ferrites: A Review

“…The radar-shielding properties of composites with Mn-Zn ferrites are caused by the small skin layer, which, in turn, is caused by a high attenuation coefficient (Equation ( 3)). The high dielectric and magnetic permeabilities of those composites originate from electrical and magnetic percolation [23,75]. One can, therefore, state that even twocomponent ferrite-polymer composites can be used as efficient RAMs in the GHz EMR range.…”

Электромагнитные свойства полимерных композитов Li-=SUB=-0.33-=/SUB=-Fe-=SUB=-2.29-=/SUB=-Zn-=SUB=-0.21-=/SUB=-Mn-=SUB=-0.17-=/SUB=-O-=SUB=-4-=/SUB=-/П(ВДФ-ТФЭ) в области частот 100-7000 МГц

“…3 представлены спектры действительной части диэлектрической проницаемости. С увеличением концентрации феррита ε ′ композитов возрастает, что коррелирует с теоретическими представлениями эффективной среды, в которой эффективная диэлектрическая проницаемость гетерогенной среды есть функция от проницаемостей отдельных компонентов [25]. Такое утверждение верно, поскольку, как видно из рисунка, диэлектрическая проницаемость полимера Ф2М составляет ∼ 3.5, а у Li-Mn-Zn-феррита ∼ 6.…”