Electrical characterisation and analysis of dominant contributions in disordered semiconducting systems with an application to the pure bentonite material for civil engineering applications

Abstract

Semiconductors and clay materials have significant applications in environmental, civil engineering and optoelectronic sectors. The application of an electric field to such systems is subject of many works. However, to understand the behaviour of such materials under the influence of an electric field, the perception of its electrical properties is essential. In the present study, the powerful technique of complex impedance spectroscopy (CIS) is introduced to illustrate the electrical characteristics of two types of disordered semiconducting materials. These are Cu₅In₉Se₁₆, an ordered defect compound of the I-III-VI₂ family and a novel bentonite clay system which is an insulator at room temperature and semiconductor above 400 °C. Na-bentonite has been studied extensively because of its strong adsorption capacity and complexation ability while Cu₅In₉Se₁₆ is considered for its use in solar and phtovoltaique domain. Some of selenides have turned out to be leading materials for electro-optical devices and the tellurides for thermoelectric power generation. It is very likely that study of bentonite clay and other similar materials may lead to the technology of heterojunction and clay composite. The frequency dependence of conductivity of bentonite was investigated using an impedance analyzer in the frequency range (20 Hz–1 MHz). The experimental data of CIS are analyzed using some analytical methods that take into account the effect of the grains and grain boundaries. The impedance data confirm the non-Debye behavior in these systems. Some important parameters related to the identified dominant contribution such as relaxation time and activation energies are estimated for the studied materials in the considered temperature and frequency ranges