Electrode Polarization Effects in Broadband Dielectric Spectroscopy

TL;DR

This paper investigates electrode polarization effects across various materials using broadband dielectric spectroscopy, revealing a universal second dispersion region linked to a second charge-transport process, and models the phenomena with a simple equivalent circuit.

Contribution

It provides a comprehensive dielectric data set for diverse materials and demonstrates a universal modeling approach for electrode polarization effects.

Findings

Universal second dispersion region observed in ionic conductors.

Excellent fits achieved with a simple equivalent circuit model.

Electrode polarization effects are significant across different material classes.

Abstract

In the present work, we provide broadband dielectric spectra showing strong electrode polarization effects for various materials, belonging to very different material classes. This includes both ionic and electronic conductors as, e.g., salt solutions, ionic liquids, human blood, and colossal-dielectric-constant materials. These data are intended to provide a broad data base enabling a critical test of the validity of phenomenological and microscopic models for electrode polarization. In the present work, the results are analyzed using a simple phenomenological equivalent-circuit description, involving a distributed parallel RC circuit element for the modeling of the weakly conducting regions close to the electrodes. Excellent fits of the experimental data are achieved in this way, demonstrating the universal applicability of this approach. In the investigated ionically conducting materials, we find the universal appearance of a second dispersion region due to electrode polarization, which is only revealed if measuring down to sufficiently low frequencies. This indicates the presence of a second charge-transport process in ionic conductors with blocking electrodes.