Li self-diffusion in garnet-type Li7La3Zr2O12 as probed directly by diffusion-induced 7Li spin-lattice relaxation NMR spectroscopy

Li self-diffusion in garnet-type Li7La3Zr2O12, crystallizing with tetragonal symmetry at room temperature, is measured by temperature-variable Li-7 spin-spin as well as spin-lattice relaxation (SLR) nuclear magnetic resonance (NMR) spectroscopy. The SLR NMR rates which were recorded in both the laboratory and the rotating frame of reference pass through characteristic diffusion-induced rate peaks allowing for the direct determination of Li jump rates tau(-1), which can be directly converted into self-diffusion coefficients D-sd. The NMR results are compared with those obtained from electrical impedance spectroscopy measurements carried out in a large temperature and wide frequency range. Taken together, the long-range diffusion process, being mainly responsible for ionic conduction at ambient temperature, is characterized by an activation energy of approximately 0.5 eV, with tau(-1)(0) approximate to 1 x 10(14) s(-1) being the pre-exponential factor of the underlying Arrhenius relation.