Dielectric properties of non-swelling bentonite: The effect of temperature and water saturation

In the present work, dielectric and conductivity measurements in the frequency range of 10 mHz-1 MHz were carried out by means of a high-resolution broadband spectrometer on non-swelling bentonite samples, at various low levels of hydration. The evolution of dielectric response was also examined after annealing of the samples up to 260 degrees C. Conductivity results in conjunction with the electric modulus representation (M*) is proved to be the Most Suitable for the analysis of the dielectric data. Dielectric response is dominated by ionic (surface and bulk) conductivity as well as by grain polarization due to migration of ions along the clay layers. Both mechanisms are strongly affected by the concentration of bound water and the thermodielectric effect. Havrilliak-Negami dielectric relaxation functions were used to model the observed relaxations mechanisms in modulus formalism and the fitting parameters were evaluated at various water contents of the measured samples. (C) 2008 Elsevier B.V. All rights reserved.