Electrical conductivity relaxation and nuclear magnetic resonance of Li conducting Li0.5La0.5TiO3

Abstract

Lithium ionic conductivity of ${\mathrm{Li}}_{0.5}$ ${\mathrm{La}}_{0.5}$ ${\mathrm{TiO}}_3$ 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${)}^{\mathrm{\beta }}$), but showing different relaxation times scales (${\mathrm{\tau }}_0$=1.4×${10}^{\mathrm{-}11}$ s from NMR and ${\mathrm{\tau }}_0$=${10}^{\mathrm{-}14}$ 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. © 1996 The American Physical Society.