Application of the Maxwell–Wagner–Hanai effective medium theory to the analysis of the interfacial polarization relaxations in conducting composite films

Abstract

A new approach to explain the interfacial polarization phenomenon in conducting composite films is proposed. HCl-doped poly(ethylene terephthalate) (PET) and polyamide-6 (PA-6) matrices with embedded polyaniline (PANI) particles as filler were investigated and analysed, combining dielectric spectroscopy and AFM electrical images with the effective medium theory analysis. Up to three relaxation peaks attributed to the interfacial polarization phenomena were detected in the studied frequency range (0.1 Hz–1 MHz). The AFM electrical images revealed that the doped PA-6/PANI composite can be modelled as a single-type particle medium and the PET/PANI one as a two-type particle medium. A simple dielectric loss expression was derived from the Maxwell–Wagner–Hanai mixture equation and was applied to the experimental data to identify the interfaces involved in each of the relaxation peaks. The parameter values (permittivity, conductivity, volume fraction of the PANI particles) were found to agree well with the measured one, hence validating the models.

Enhanced dielectric properties of PVDF-HFP/BaTiO3-nanowire composites induced by interfacial polarization and wire-shape

“…The enhancement is clearly greatest for the ellipsoidal inclusions because of their larger dipole moments (versus spherical shapes). [56][57][58] The comparison of PVDF-HFP/BT-NWs and PVDF-HFP/BT-NPs composites is plotted in Fig. 13.…”

Nanoparticle, Size, Shape, and Interfacial Effects on Leakage Current Density, Permittivity, and Breakdown Strength of Metal Oxide−Polyolefin Nanocomposites: Experiment and Theory

“…For spheres, all three depolarization factors are equal ( 1 / 3 , 1 / 3 , 1 / 3 ), and for ellipsoids (infinite needles) the depolarization factors are 0, 1 / 2 , 1 / 2 , respectively (1, 0, 0, respectively, for discs). For the case of spherical inclusions, the effective permittivities are estimated using the Maxwell−Garnett (MG) effective medium theory (eq ), , and for the case of randomly aligned ellipsoidal inclusions, the effective permittivities are estimated using the Polder−Van Santen (PVS) formalism (eq ), where ε a is the relative permittivity of the TiO 2 inclusions, ε b the relative permittivity of isotactic polypropylene, f a the volume fraction of TiO 2 , and the N j represents the depolarization factors ε eff = ε b [ normalε normala + 2 normalε normalb + 2 f normala false( normalε normala − normalε normalb false) normalε normala + 2 normalε normalb − f normala false( normalε normala − normalε normalb false) ] ε eff = ε b + f a 3 ( ε a − ε b ) …”

Two‐dimensional dielectric imaging for dermatologic screening: a feasibility study

“…This research presented herein extends that earlier work through testing in a dermatologic application. The underlying theory on which this detection method is based is termed Maxwell–Wagner theory, sometimes referred to as relaxation theory . Briefly, this theory states that large frequency‐dependent contributions to the dielectric response – especially in the so‐called β‐region (corresponding to 10 4 –10 8 Hz) – may result from charge accumulation at an interface between two dissimilar layers within a sample.…”