The use of electron paramagnetic resonance in the probing of the nano-dielectric interface

Electron paramagnetic resonance (EPR) has been used to study the properties of trapped electrons or holes in XLPE and in 12.5% vinylsilane-treated SiO₂ nano-particles in XLPE specimens. Both electrically unstressed and electrically stressed (up to 25 kV/mm) specimens were used. The EPR spectra of both materials indicated that the acceptors/donors were oxygen radicals in the polymer, probably originating during the cross-linking. It was found that the anisotropic oxygen environments were not randomly oriented, but were textured, presumably during the fabrication of the sheet specimens. It was found that under the action of an applied electric field, the population of an additional number of oxygen radicals occurred. This result is discussed in relation to the implied polymer structure and conductivity mechanisms.