Origin of constant loss in ionic conductors

Abstract

We have analyzed the constant loss contribution to the ac conductivity in the frequency range 10 Hz–1 MHz and temperatures down to 8 K, for two Li ionic conductors, one crystalline (Li_(0.18)La_(0.61)TiO_(3)) and the other glassy (61SiO_(2) . 35Li_(2)O . 3Al_(2)O_(3) . P_(2)O_85)). As temperature is increased a crossover is observed from a nearly constant loss to a fractional power law frequency dependence of the ac conductivity. At any fixed frequency ω, this crossover occurs at a temperature T such that ω = v_(0) exp(-E_(m)/k_(B)T), where v_(0) is the attempt frequency and E_(m) is identified with the barrier for Li^(+) ions to leave their wells.