Non-Debye conductivity relaxation in the non-Arrhenius Li0.5La0.5TiO3 fast ionic conductor.: A nuclear magnetic resonance and complex impedance study

An analysis of electrical conductivity relaxation and nuclear magnetic resonance spin-lattice relaxation has been conducted to study the dynamics of the ionic diffusion process in the crystalline ionic conductor Li0.5La0.5TiO3. Dc conductivity shows a non-Arrhenius temperature dependence, similar to the one recently reported for some ionic conducting glasses. Taking into account this non-Arrhenius dependence for the relaxation times, spin-lattice and conductivity relaxations are compared in the same frequency and temperature ranges. A single "stretched exponential" relaxation function of the form f(t) = exp(-(t/tau)(beta)), with beta = 0.4, can be used to describe both relaxation processes in which correlation times differ in the preexponential factor. (C) 1998 Elsevier Science B.V. All rights reserved.