Temperature dependence of the electrical conductivity in EMIM-based ionic liquids -: Evidence of Vogel-Tamman-Fulcher behavior

We present measurements of the electrical conductivity versus temperature for six pure 1-ethyl-3-methyl imidazolium (EMIM) based ionic liquids (ILs) at atmospheric pressure. The temperature range measured goes from 250 to 430 K, although the exact range for each IL varies depending on its melting and vaporisation temperatures. The data measured shows that the electrical conductivity value for all ILs, except EMIM-BF4, increases more than 200 times for temperature increases of 180 K. We have also observed that the temperature dependence of the electrical conductivity for all measured ILs can be fitted with high precision with a Vogel-Tamman-Fulcher (VTF) type equation. From the fitting parameters we will extract the activation energy and the glass transition temperature. (c) 2006 Elsevier B.V. All rights reserved.