Maxwell-Wagner-Sillars interfacial polarization in dielectric spectra of composite materials: Scaling laws and applications

Abstract

An experimental and theoretical investigation of the scaling laws governing the phenomenon of Maxwell-Wagner-Sillars interfacial polarization in composite materials in dependence on morphology, volume fraction, orientation of fillers, form factor and the presence of interphases is presented in the current study. By considering the complex dielectric function of the matrix and of the fillers, the dielectric spectra are calculated in the frequency range from 107 Hz to 10-2 Hz and compared to dielectric measurements by Broadband Dielectric Spectroscopy, carried out in the frequency range from 107 Hz to 0.5Hz and between -90oC and 150oC. The characteristic frequencies of the global dielectric response are reported to strongly vary with the conductivity value of the conductive phase, while a much weaker dependence is observed upon varying the volume fraction, the form factor and the orientation of fillers. The value of permittivity at low frequency does not change with the conductivity value, whereas a significant variation is observed in dependence on the composite morphology, form factor, orientation of fillers and presence of interfaces with different gradients of properties. Two possible applications of our analysis are reported: (i) measuring the conductivity of materials without employing a direct electrical contact between the electrodes and the sample and (ii) discriminating different phenomena of electrical polarization in complex materials by analyzing the scaling laws. Our study delivers thus a useful and necessary analysis of the dielectric behavior of composite materials, where interfacial polarization effects play a major role.

Employing impedance spectroscopy to investigate electrical conduction mechanism in polymer composite blends containing conductive masterbatch: PP/EVA/ (PP-g-MA/MWCNTS)

“…According to Maxwell-Wagner-Sillars theory, an increase in the interfacial polarization of polarizable dipoles occurs, and subsequently dielectric constant increases. 57 In Figure 8(b) the slope of dielectric loss against frequency shows how electrons are conducted through the samples. Electron conduction is controlled by direct contact, as much as the slope of this graph is close to 1, otherwise, electron tunneling is dominant.…”

Photocurable Hybrid Materials with High Magnetodielectric Coupling

“…Figure shows that the frequency dependence of the dielectric behavior is similar for all samples independently of the filler content (also independently of the filler type as Figure S5 reveals), being characterized by a decrease of the dielectric constant with increasing frequency due to the slow dipole relaxation. , In the case of the composites, interfacial polarization is dominant at lower frequencies due to large surface/volume ratio. Considering the Maxwell–Wagner–Sillars (MWS) theory of interfacial polarization and Koop’s phenomenological theory, small-sized nanoparticles lead to a large number of grain boundaries based on the large specific surface area, which results in interfacial carrier accumulation and confined vibration in the interfaces with the applied field. In the case of ferrites (as CFO and Fe 3 O 4 ), charge carriers originate mainly from the electronic exchange between Fe 2+ and Fe 3+ and/or the hole transfer between Co 2+ and Co 3+ in the spinel phase .…”

“…21,38 In the case of the composites, interfacial polarization is dominant at lower frequencies due to large surface/volume ratio. Considering the Maxwell−Wagner− Sillars (MWS) theory of interfacial polarization 39 and Koop's phenomenological theory, 40 small-sized nanoparticles lead to a large number of grain boundaries based on the large specific surface area, 41 which results in interfacial carrier accumulation and confined vibration in the interfaces with the applied field. In the case of ferrites (as CFO and Fe 3 O 4 ), charge carriers originate mainly from the electronic exchange between Fe 2+ and Fe 3+ and/or the hole transfer between Co 2+ and Co 3+ in the spinel phase.…”

Advantages and limitations of active phase silanization in PVDF composites: Focus on electrical properties and energy harvesting potential

“…(1) polarization due to the accumulation of space charge in the interface region between PVDF matrix and filler particles and/or (2) polarization at the boundaries between the crystalline and amorphous PVDF phases. 40,[44][45][46] Interfacial polarization in non-modified samples is higher than in modified samples. In the latter, the filler particles are anchored to the PVDF matrix through the silane coupling agents, that lowers the interfacial tension between particles and polymer.…”