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. Four matrix materials, polymer and ceramic dielectrics with a different dielectric permittivity were used in the experiments: polystyrene (PS525), polyvinylidene fluoride (grade F2MB), lead zirconate titanate (ZTS-21), and barium titanate (TBK-3). Experimental samples of composites were obtained by hot (for a polymer matrix) or cold pressing with a binder (in case of ferroelectric ceramic matrix). It has been shown that the microwave-absorbing properties of the resulting composites significantly depend on the electrical properties of the dielectric matrix and the electrical resistivity of the filler. The highest attenuation of electromagnetic waves of 25 – 27 dB in the frequency range 4 – 5 GHz is observed for ferrite-polymer composites with a semiconductor filler of 2000NM with a thickness of microwave-absorbing material of 6 mm. For composites with Mn-Zn ferrite filler, 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 shifted to the low-frequency region 1 – 4 GHz with a maximum attenuation of up to 22 dB at the same thickness. It was experimentally confirmed that at a concentration of ferrite Cm = 40 % wt., the value of the frequency of absorption peal center fc and the minimum value of the reflection loss Kref for a filler with high electrical resistance of 2000NN decrease with an increase in the dielectric constant of the matrix. As for the composites with a 2000NM filler, the (ε’ of the matrix) dependence passes through a minimum. The obtained composites can be considered as effective microwave-absorbing materials for the frequency range 1 – 6 GHz with peak attenuation of the electromagnetic wave in the range 14 – 27 dB and frequency band (less than 10 dB) in the range 1.1 – 2.5 GHz.