Solid Electrolytes: Jump Relaxation and “Universal” Dynamic Response

Abstract

AbstractIn solid ionic conductors, the hopping motion of the mobile charged defects is strongly influenced by their mutual repulsive interaction. Therefore, their jump diffusion ist not a random process. Instead, correlated forward-backward hopping sequences are a common phenomenon, constituting the elementary steps of jump relaxation. The microscopic dynamics of the relaxation is described in a simple model which yields the frequency spectrum of the hopping motion. With the help of this function, it is possible to explain experimental spectra displaying the so-called “universal” dynamic response. In particular we reproduce the frequency dependent ionic conductivity of fast ion conductors and the arcs in their complex-conductivity and complex-permittivity planes. The model also explains the non-BPP-type behavior of spin-lattice relaxation times and the broad components of quasielastic neutron scattering spectra. Examples are presented and discussed.