Diffusion of Li ion in glassy Li2O·B2O3 system

The ionic migration in lithium borate glasses with various composition of molar ratio R (R=0.15, 0.21, 0.33, 0.5, 0.7, 1 and 1.4) is studied by the conductivity and the nuclear magnetic resonance techniques. Four activation energies for Li ion migration characterizing these observed quantities, Eσ determined from dc conductivity, Ep from ac conductivity, Eδω from motional narrowing phenomenon in nmr and ET1 from spin lattice relaxation rate, are obtained. Relation between these energies is discussed. The prediction of the coupling model Eσ<Eδω∼ET1 does not hold. Applying a trapping model, the temperature and R dependence of ionic jump time are calculated and the results can explain successfully the experimentally determined ionic jump time τnmr for the glasses with R>0.33. The model cannot be applied to the glasses (R<0.21) in which percolation transition in the hopping rate appears.