Impedance measurements on LiCl-Al2O3-SiO2 xerogels

Abstract Impedance spectroscopy was employed to determine the electrical properties of LiCl-containing Al 2 O 3 -SiO 2 gels prepared by the sol-gel method. Measurements were carried out in the frequency range of 1 Hz to 1 MHz under dynamic vacuum. The impedance was determined at various temperatures on cooling, after first heating the samples to 230 °C. Two thermally activated bulk processes were detected in the xerogels. These two processes could be resolved by plotting the imaginary part of the electric modulus, M ″, against the logarithm of the frequency. It was possible to estimate the activation energies associated with each process. The activation energy of one of the responses corresponds to that of crystalline LiCl ( E a = 0.80 ±0.05 eV). The value of the second activation energy varies with LiCl content in the gels. The enhancement in conductivity for the gels as compared to LiCl alone is analogous to that found in ceramic composite electrolytes such as Lil-Al 2 O 3 and Lil-SiO 2 .