Low frequency internal friction study of lithium ion conductor Li5La3Ta2O12

The diffusion processes of lithium ions in Li5La3Ta2O12 based electrolytes were investigated by internal friction (IF) method. Prominent relaxation-type IF peaks (actually consisted of two components) in Li5La3Ta2O12 were observed: peak P1 at lower temperature and peak P2 at higher temperature. The relaxation parameters for the IF peaks are evaluated as E1 = 0.81 eV, τ01 = 2 × 10−14 s for peak P1 and E2 = 0.87 eV, τ02 = 7 × 10−14 s for peak P2, respectively. After partial Ba substitution at La site (Li6BaLa2Ta2O12), peak P2 decreases dramatically in height while peak P1 does not change in height, but both peaks shift toward lower temperature. The mechanism of the P1 and P2 peak is suggested to be associated with two diffusion processes of lithium ions: 48g ↔ 48g and 48g ↔ 24d, respectively.