Dielectric relaxation dynamics in C 60 and C 70

Abstract

The electrical response of polycrystalline fullerites has been studied after annealing them under various conditions. Dielectric measurements have been carried out in the frequency range 100 Hz < ν < 1 MHz and for temperatures 10K < T < 300 K. For C 60, electronic conduction, a phase transition and a dielectric relaxation process are clearly resolved. The latter is described by simple thermally activated behaviour but a broad spectrum of relaxation times, the origin of which is discussed. For C 70, no clear experimental evidence for a similar dielectric relaxation process could be found in the temperature and frequency regime investigated.