CONDUCTIVITY AND DIELECTRIC-RELAXATION IN HYDRATED FUSED-SALTS

The dielectric properties of Ca(NO3)2.2.9H2O, Cd(NO3)2.2.37H2O and (Ca + Cd)(NO3)2.2.92H2O have been measured in the supercooled liquid stat e immediately above their respective calorimetric glass-transition tem peratures. Over the frequency range 12-10(5) Hz, their permittivity an d loss spectra are featureless. By subtracting the contributions from electrode impedance and dc conductivity, the remaining epsilon, which is due to a polarization process, is described well by a Davidson-Col e relaxation function with beta in the range 0.26-0.40 (+/-0.05). The activation energies for conduction are 200-220 kJ mol-1. Beta decrease s with decreasing temperature, as does the contribution to permittivit y from orientation polarization. The latter, which differs from the be haviour of most liquids, indicates a decrease in the number densities of the molecular and ion-pair dipoles and/or their dipole moments with decreasing temperature. Analyses of the data in epsilon and M* (=eps ilon-1) formalisms give the same results. The former is direct, altho ugh it requires knowledge of the exponent for the electrode impedance. The data also fit an asymmetric distribution of conductivity relaxati on times at least as well as in the literature, but this fit appears t o be misleading.