AC Properties of a Random Barrier Network

Abstract

The ac properties of random barrier network are analyzed using the effective medium theory.At low frequencies om -cus and a t high frequencies i t saturates to the value determined by the conductivity of the bulk material. Below the percolation threshold s N 0.8, a t the threshold s zz 0.4, and above the threshold s still decreases. The effective dielectric constant P, decreases with increasing frequency saturating to the bulk value a t high frequencies. At, the percolation threshold em shows a pronounced maximum exceeding by several orders of magnitude the bulk value.Die Wechselstromeigenschaften des Random-Barrieren-Netzwerks werden mittels der Effektiv-

DC and AC Conductivity in Polymeric Particulate Composites of Epoxy Resin and Metal Particles

“…It is also higher in composites with greater Ni content. This behaviour is shown by a conducting network if barriers are randomly distributed, so that its AC properties are consistent with a resistor-capacitor network model [11]. From the temperature shift of ù c , since ù c ~ exp (-eV/kÔ), the barrier height can be calculated for the composites of this work.…”

“…The conductivity of these disordered conductor-insulator composites is strongly frequency dependent [8,9]. Several approaches based on effective medium theory [10,11] or hopping transport [12] lead to similar results. They predict the frequency dependence of the conductivity to be σ ∼ω s with the exponent having a value close to unity but temperature dependent increasing with decreasing temperature [10].…”

The microwave cavity perturbation technique for contact-free and in situ electrical conductivity measurements in catalysis and materials science

“…22,23 Therefore, the DC conductivity s DC is determined mainly by the height and width of the intergrain barriers and not by the intrinsic electronic properties of the grains. In contrast, with AC (or microwave) measurements the grain boundaries become increasingly shunted by capacitive coupling between conducting grains with increasing frequency, and thus the contribution of the grain conductivity to the measured value increases.…”

“…In contrast, with AC (or microwave) measurements the grain boundaries become increasingly shunted by capacitive coupling between conducting grains with increasing frequency, and thus the contribution of the grain conductivity to the measured value increases. 22,23 Alternatively, the conduction process can be described for some materials by a hopping mechanism, where electronic or ionic conduction is characterized on an atomistic scale by activated hopping of charge carriers between localized states. [22][23][24] Both the barrier and the hopping model predict the following frequency dependence of the conductivity for a rather wide frequency range:…”

“…22,23 Alternatively, the conduction process can be described for some materials by a hopping mechanism, where electronic or ionic conduction is characterized on an atomistic scale by activated hopping of charge carriers between localized states. [22][23][24] Both the barrier and the hopping model predict the following frequency dependence of the conductivity for a rather wide frequency range:…”