Non-Arrhenius temperature dependence of conductivity in lanthanum lithium tantalate

Non-Arrhenius temperature dependence of bulk dc conductivity was observed in La1/3-xLi3xTaO3 which are Li-ion conductors derived from A-site deficient perovskites. In order to discuss the non-Arrhenius conductivity, several parameters relevant to the Li ion dynamics were determined by impedance spectroscopy and Li-7 NMR. The activation energies of the dc conductivity in the high and low temperature ranges were nearly equal to that of the reciprocal correlation time (f(NMR)) obtained from NMR measurement and that of the crossover frequency (f(p)) extracted from a power-law analysis of conductivity spectra, respectively. A change in the activation energy of the dc conductivity occurred in the vicinity of temperature where f(p) is equal WAMR. Because f(p) relates to correlated hops of mobile ions and f(NMR) to non-correlated hops, our result supports Ngai's explanation which premises presence of a microscopic time.