Electrical conductivity relaxation and nuclear magnetic resonance of Li conducting Li_(0.5)La_(0.5)TiO_(3)

Abstract

Lithium ionic conductivity of Li_(0.5)La_(0.5)TiO_(3) has been studied using nuclear magnetic resonance (NMR) and admittance spectroscopy (AS) techniques. Spin-lattice relaxation and electrical conductivity relaxation are well described in terms of stretched-exponential correlation functions in the time domain of the form φ(t) = exp(-(t/τ) (β), but showing different relaxation times scales (τ_(0) = 1.4 x 10^(-11) s from NMR and τ_(0) = 10^(-14) s from AS), and activation energies (0.15 and 0.4 eV, respectively). Different β exponents, 1 from spin lattice relaxation and 0.4 from electric-field relaxation have been also deduced. A microscopic activation energy for lithium motion of 0.15 eV is deduced from both techniques. Discrepancies between both techniques are analyzed and discussed in terms of frequency-dependent correlation effects.