Anormalous frequency-dependent conductivity in DC regime and long correlation length among mobile ions of β-alumina

Electrical conductivity measurements of single crystals Na, Ag, Rb and Cd β-alumina have been performed in the frequency range 10⁻²~10⁷ Hz. Na β-alumina and Ag β-alumina are well known as “super”ionic conductor. Rb β-alumina and Cd β-alumina are “ordinary” solid electrolytes. The magnitude of conductivity depends on the kind of mobile ion strongly. One diffusion step of an ion will result in a change of the local potentials by the ion itself and by its neighbours. The motion of the mobile ions has to be regarded as a highly correlated process under many-particle effects. The present systematic investigation between “super”ionic conductor and “ordinary” solid electrolyte provided an experimental evidence of the many-particle effects in the long-range diffusion. The application of fractal concept for a random walk was helpful us to see the physical means of ion dynamics in the superionic conductor.