Charge transport and dipolar relaxations in an alkali metal oligoether carboxylate ionic liquid

Charge transport and dipolar relaxations in a sodium-based oligoether carboxylate ionic liquid are investigated in a wide frequency and temperature range by means of broadband dielectric spectroscopy (BDS). The dielectric spectra are described at lower temperatures in terms of dipolar relaxations whereas hopping conduction in a random spatially varying energy landscape is quantitatively shown to dominate the spectra at higher temperatures. Based on detailed analysis of the dielectric relaxation strength in its temperature dependence, the slower secondary relaxation process is attributed to molecular fluctuation of ion pairs (sodium and carboxylate ions) while the localized motion of the carboxylate anion gives rise to the faster process observed.