Li self-diffusion in garnet-type Li7La3Zr2O12as probed directly by diffusion-inducedLi7spin-lattice relaxation NMR spectroscopy

Abstract

Li self-diffusion in garnet-type Li${}_{7}$La${}_{3}$Zr${}_{2}$O${}_{12}$, crystallizing with tetragonal symmetry at room temperature, is measured by temperature-variable $^{7}\mathrm{Li}$ 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 ${\ensuremath{\tau}}^{\ensuremath{-}1}$, which can be directly converted into self-diffusion coefficients ${D}_{\mathrm{sd}}$. 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 ${\ensuremath{\tau}}_{0}^{\ensuremath{-}1}\ensuremath{\approx}1\ifmmode\times\else\texttimes\fi{}{10}^{14}$ ${\mathrm{s}}^{\ensuremath{-}1}$ being the pre-exponential factor of the underlying Arrhenius relation.