Determination of the very low-frequency characteristics of dielectric materials: A surface potential approach

Abstract

A new approach using surface potential measurements for low-frequency characterization of dielectric materials is proposed. In fact, isothermal surface potential decay measurements are often used to characterize both surface and bulk properties of dielectric materials. A lot of work has been devoted to correlate these potential decays to physical mechanisms, when superficial conductivities can be neglected. In most cases, charge injection has been considered; however, following either sample thicknesses or low applied electric field, these decays may be related to the absorption current of the material. A close correlation relating the derivative of the surface potential to the absorption current is established. The frequency characterization is then achieved using Fourier transformation. In order to validate it, this method is applied to different kinds of material such as coatings or epoxy based composites. It allows one to determine, for composite materials, the existence of very low-frequency relaxation associated with interfacial phenomena. A final validation is achieved using the Kamers–Kronig test. This new approach provides the study of the reinforcement morphology or volume fraction on the permittivity spectra. It may also be used in different physical fields. An example concerning corrosion detection is given but this technique may also be applied in the study of electrical aging.