Abstract
We have investigated the conduction phenomena in compacted tablets of cellulose with varying relative humidity (RH) with techniques such as Low Frequency Dielectric Spectroscopy (LFDS) and Transient Current (TC) at room temperature. Two exponential decaying regions in the transient current measurements indicate two ionic species contributing to the conduction mechanism. A high powerโlaw exponent of โผ9 for the conductance with moisture content has been found. The mobility initially decreases with RH up to monolayer coverage, and further water vapor increases the mobility, indicating a blocking of available positions for the charge carrier ions. When the amount of water molecules present in the tablet increases one order of magnitude, the number of charge carriers increases 5โ6 orders of magnitude, suggesting a transition from a powerโlaw increase to a linear effective medium theory for the conduction. The charge carrier dependence on RH suggests that a percolating network of water molecules adsorbed to 6โOH units on the cellulose chain span through the sample. The conductivity mechanisms in cellulose are still not clear. (ยฉ 2006 WILEYโVCH Verlag GmbH & Co. KGaA, Weinheim)