Abstract
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 Li6BaLa2Ta2O12 (LBLT) and Li5La3Ta2O12 (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 x 10(21) and 6.71 x 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.