The conductivity of various alkali silicate, borate and germanate glasses was measured at temperatures ranging from 3 to 100K (10 to 100kHz). It was found that, in general, the frequency and temperature dependence of the conductivity below 150K could be described by   T, where  was between 0 and 0.25 and  was between 1 and 1.15. An abnormal decrease in conductivity with increasing temperature was observed at 100 to 150K in glasses with alkali oxide contents of less than 1mol%. A theoretical model which was based upon the thermally activated excitation of asymmetrical double well potential configurations was used to explain the low-temperature conductivity data. From the alkali concentration and the size dependence of the parameters in the above model, a physical description of the species which was responsible for low-temperature alternating current conductivity was obtained.

X.Lu, H.Jain: Journal of the Physics and Chemistry of Solids, 1994, 55[12], 1433-43