The study of molecular movements in dielectrics using isothermal and non-isothermal current measurements

Abstract

The electrical methods used to study the molecular movements in dielectric materials are based on the movement of the dipoles, which are parts of the component molecules, under a convenient external applied DC or AC electric field. We have proposed recently a combined isothermal and non-isothermal measuring protocol to analyze charge injection/extraction, transport, trapping and de-trapping in low mobility materials. During an electric polarization process or an electric charging process, besides the polarization process, electric charge is injected into the material. This charge is partially transported and partially trapped in the material, depending on the material properties and on the experimental conditions. As a consequence of the charge trapping process, the structure is decorated with space charge and during the subsequent thermally stimulated discharge current experiment we are observing an apparent peak and the genuine peaks that are related to dipole randomization and charge de-trapping determined by the molecular movements. The aim of this paper is to present a combined measuring protocol that allows to separate the apparent peak and the genuine peaks in polar and non-polar dielectric materials. The method is very sensitive, very selective and allows to reveal, in a single run, details that are not observed when other electrical and non-electrical techniques are used.