Distribution of activation energies explains ionic motion in glassy fast ion conductors: Li-7 NMR spin-lattice relaxation and ionic conductivity in xLi(2)S+(1-x)GeS2

We report Li-7 nuclear spin-lattice relaxation (NSLR) measured at 4, 12.1 and 22 MHz, and conductivity measured from 1 Hz to 10 MHz from 100 to 500 K, on a series of xLi(2)S + (1-x)GeS2 glasses with x = 0.35, 0.45 and 0.55. These data were used to examine the quality of the model for the ionic motion and the ionic conductivity in Li+ glassy fast ion conductors (FIC) obtained by describing the ionic hopping motion with a distribution of activation energies (DEA) derived from the Li-7 NSLR. We find that the distribution of activation energies obtained from NMR and the percolation threshold in the barrier distribution obtained from conductivity are a function of the composition of the glass.