Relaxation in mixed alkali fluoride glasses

We have investigated the dynamics of alkali cations as well as fluorine anions in non-oxide fluoride glasses with a total alkali fluoride content varying from 16 to 35 mol% in the frequency range from 10 Hz to 2 MHz and in the temperature range from room temperature to just below the glass transition temperature. We have shown that the dc and ac conductivity, crossover frequency and conductivity relaxation frequency exhibit a minimum in mixed alkali fluoride glasses, where anions also participate in the diffusion processes in addition to cations, unlike mixed alkali oxide glasses and crystals. We have observed lower dimensionality of the conduction pathways in mixed alkali fluoride glasses compared to that in the single alkali glasses. We have shown that the relaxation dynamics in mixed alkali fluoride glasses is independent of temperature.