Analysis of the Electromagnetic Properties of 2000NN/2000NM Composites with Ferroelectric and Polymer Matrices

The results of studying the electrical properties of ferrite-dielectric composites containing inclusions of Mn-Zn and Ni-Zn spinel ferrites with the same initial magnetic permeability (grades 2000NM and 2000NN, respectively) and different electrical resistance are presented. Polymer and ceramic dielectrics with different values of dielectric permeability were used as matrices of composites: polystyrene (PS525), polyvinylidene fluoride (grade F2MB), lead zirconate titanate (PZT-21), and barium titanate (TBK-3). Experimental samples of composites were obtained by hot pressing (for a polymer matrix) or cold pressing with a binder (for a ferroelectric ceramic matrix). It has been shown that the radio-absorbing properties of the obtained composites strongly depend on the electrical properties of a dielectric matrix and on the electrical resistivity of a filler. The highest attenuation of electromagnetic waves of 25–27 dB in the frequency range of 4–5 GHz is observed for ferrite-polymer composites with a 2000NM semiconductor filler with a 6-mm-thick radio-absorbing material. For composites filled with a Mn-Zn ferrite, a pronounced shift in the dispersion region of magnetic permeability is also observed, which in turn changes the frequency position of peak radio absorption. For the composites with a ferroelectric matrix, the operating frequency range for both fillers was shifted toward the low-frequency region of 1–4 GHz with maximum attenuation of up to 22 dB at the same thickness of the material. It was experimentally confirmed that, at a weight content C_m of ferrite of 40 wt %, an increase in the dielectric permeability of the matrix results in a decrease in frequency f_c of the center of minimum absorption and in a decrease in minimum reflection coefficient \(K_{{{\text{refl}}}}^{{\min }}\) at a metallic plate for a 2000NN filler with a high electrical resistance. For the composites with a 2000NM filler, the dependence of \(K_{{{\text{refl}}}}^{{\min }}\) (ε' of the matrix) passes through a minimum. The obtained composites can be considered as effective radio-absorbing materials for the frequency range of 1–6 GHz with peak attenuation of an electromagnetic wave in the range of 14–27 dB and with the operating frequency band of 1.1–2.5 GHz (at a level less than 10 dB).