On the sign of the relaxation activation energy for interfacial polarization in reduced graphene oxide-based nano-composites

摘要

The dielectric relaxation mechanism associated with the interfacial polarization in polyaniline/ reduced graphene oxide (PANI/RGO) nano-composites is found to shift towards lower frequencies on increasing temperature. Accordingly, the effective activation energy value is negative. Basic concepts of the Sillars dielectric theory of a heterogeneous medium are revisited for a material consisting of conducting platelets dispersed in a semi-insulating matrix in order to explain the negative sign of the relaxation energy. A plausible explanation to this observation involves a thermally activated de-trapping mechanism through the effective potential barrier at the interfaces between RGO and PANI. This results in an enhancement of the density of charge carriers which contributes to dc conductivity at the expense of the density of charge carriers that relax within RGO inclusions. Subsequently, the intensity of the dielectric peak is suppressed on heating which results in a systematic modification of the shapes of the dc conductivity vs temperature curves.