Concentration and mobility of mobile Li+ ions in Li6BaLa2Ta2O12 and Li5La3Ta2O12 garnet lithium ion conductors

The concentration of mobile ions, n c , and their mobility are important factors that control the conduction process in ionic conductors. The analysis of the conductivity spectra of Li 6 BaLa 2 Ta 2 O 12 (LBLT) and Li 5 La 3 Ta 2 O 12 (LLT) Li + conducting garnets at low temperatures helps us to estimate the values of n c of Li + ions and their mobility. We found that n c is independent of temperature with an average values of 1.93 × 10 21 and 6.71 × 10 20 cm −3 for LBLT and LLT, respectively. These values of n c represent only a small fraction of 8.79 % (in LBLT) and 3.52 % (in LLT) out of the total Li + ions content. Our results confirm that the conduction process is controlled by the mobility of Li + ions, which is related to the occupancy of Li + in the tetrahedral sites of the garnet phases. Moreover, the diffusivity of Li + has been estimated at different temperatures and compared to other fast Li + conductors.