Conductivity and Dielectric Relaxation in Concentrated Aqueous Lithium Chloride Solutions

Abstract

This paper describes a study of the recently recognized phenomenon of conductivity relaxation in liquid electrolytes as it is observed in the system $\mathrm{LiCl+water}$ . Advantage has been taken of the supercooling ability of 6–20m solutions in this system to reduce solution temperatures to the vicinity of −100°C and thereby to increase the relaxation time characteristic of the conductance process sufficiently to permit its study with conventional ac conductance bridges operating in the frequency range 0.2–2 000 kHz. Extensive data are presented for four solutions in the concentration range 8.3–11.9m. When the frequency‐dependent conductance and capacitance data are analyzed in the dielectric modulus notation developed by Macedo, Bose, and Litovitz, mean relaxation times for conductance are obtained which have a non‐Arrhenius temperature dependence identical to that of the dc conductivity. Earlier studies of dielectric relaxation in these solutions, carried out at room temperature and gigahertz frequencies, are re‐analyzed and shown to correspond to the high‐temperature extension of the same phenomenon examined at low temperatures in the present study. The characteristic migration distance associated with the conductivity relaxation time, assessed using the Nernst—Einstein equation, is of ionic dimensions. The presence of subsidiary higher‐frequency relaxations is noted and their origin considered in relation to Goldstein's ubiquitous ``localized motions'' in glasses.