Study of the relaxation and resonance behaviors of ternary composites: Epoxy–strontium titanate–carbon black
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.