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The purpose of this article is to study the dielectric dispersion of two different ternary composites made of epoxy resin (RE), black iron oxide (Fe3O4) with one of the two titanates (calcium titanate (CaTiO3) or strontium (SrTiO3)) on several frequency bands. Additionally, the effect of the two titanates and the (Fe3O4) on the permittivity and conductivity of these ternary composites is investigated. These composite materials were characterized using time domain spectroscopy (TDS). The inclusion of the two titanates increased the real permittivity and conductivity of the two composites, shifting the resonance frequency (ƒR) towards the low frequency range and causing the opposite phenomenon for the static permittivity (ε s). The frequency dispersion behavior model for the complex permittivity has been proposed to improve the effectiveness of the predictive frequency model through a better choice of the damping factor and to bring theoretical and experimental findings closer together. Comparing these data shows that the proposed model is applicable to ternary combinations with high accuracy. The values of the quality factor (Q) obtained are encouraging in microwave applications. These composite materials witch containing CaTiO3 and SrTiO3 inclusions have contributed to the development of dielectric permittivity that suits very well frequency communication systems.

The principal subject of the present article is the study of the phenomenon of dispersion as well as the effect of the concentration of strontium titanate (SrTiO3) and carbon black on the complex permittivity of ternary composites: epoxy resin–SrTiO3 –black carbon. The relative permittivity of the mixtures as a function of volume fraction of SrTiO3 was modeled by the modified Lichtenecker mixing law (MLL). A new dispersion model, based on the Lorentzian resonance model, has been proposed to describe the frequency behavior of complex permittivity. For these ternary composites, the frequency dispersion behavior of the complex permittivity that exhibits both relaxation and resonance spectra with increasing SrTiO3 concentration has been showed. The new empirical equation proposed in our work has been well describing the complex permittivity of resonance type for the SrTiO3 and carbon black composites. The effects of SrTiO3 content on the electromagnetic properties and absorption characteristics of electromagnetic waves of epoxy resin composites were studied. As the volume fraction of SrTiO3 increases, it was confirmed that the complex permittivity of the composites follows the MLL and the resonant frequency shifted toward the high frequency range. The resonance frequency of the composites was estimated in good agreement with the theoretical values calculated by the second new equation proposed in this article. Complex permittivity is measured using time domain spectroscopy in the frequency range direct current (DC) to 30 GHz.

The RE-ST-FE and RE-BT-FE/FR composites have been prepared and characterized using time domain spectroscopy method in the [DC-12.5] GHz range. The dielectric, magnetic, and electrical properties of the ternary composites have been investigated. In the RE-ST-FE composite, the dielectric permittivity (ε’) has been found to decrease from 9.25 to 3.70 with increase in FE concentration. While it has been observed that the electrical conductivity increases as the ST concentration increases reaching a value of 11.6 (mS / m) and shows a percolation behavior with (Vth = 26,9% ST). In the RE-BT-FE/FR composites, the magnetization hysteresis loops have been measured by vibrating sample magnetometer from -3 to +3 kOe. This has made it possible to have a maximum of saturation magnetization equal 29.3 emu/g and the permeability value close to 1.9 with the RE-BT-FR composite which is considered higher than that of the other one. It was found that an increase in the (FE/FR) concentration increases the magnetic permeability, which is confirmed by the modified Lichtenecker law with error ratio less than 0.5%. The results of this study will undoubtedly yield new materials that can be used to miniaturize electronic components used in telecommunications systems, resonators, antennas and wave absorbers.