Activation energy of polarization due to electrical conductivity and dipole rotation in purified ca-bentonite

We determined the activation energy for dipole rotation and electrical conductivity by analyzing the frequency dependent dielectric permittivity measurements of purified Ca-Bentonite. The measurements were performed at four different temperatures between 296 K and 353 K and at frequencies between 5 Hz to 5 MHz. We used the Havriliak–Negami (HN) relation to represent the polarization due to dipole orientations and the Maxwell–Wagner–Sillars (MWS) relation with a power law term to represent the interfacial polarization. We obtained expressions for the real and imaginary parts of electric modulus M*(ω).We determined the relaxation times for HN and MWS contributions from a fit of the experimental data. Subsequently, the activation energies for HN and MWS contributions were obtained from an Arrhenius plot. The activation energy for the HN and MWS processes were found to be 22.3 kJ/mol and 18.2 kJ/mol, respectively.

► Frequency dependent dielectric properties of a purified Ca-bentonite were measured. ► Th effect of orientational and interfacial polarizations were taken into account. ► The apparent activation energies were determined for the HN and MWS models.