Spin-alignment echo NMR: probing Li+ hopping motion in the solid electrolyte Li7La3Zr2O12 with garnet-type tetragonal structure **Dedicated to Professor Dr Paul Heitjans on the occasion of his 65th birthday.

Abstract

7Li spin-alignment echo (SAE) nuclear magnetic resonance (NMR) spectroscopy has been used to measure single-spin hopping correlation functions of polycrystalline Li7La3Zr2O12. Damping of the echo amplitude S2(tm,tp), recorded at variable mixing time tm but fixed preparation time tp, turns out to be solely controlled by slow Li jump processes taking place in the garnet-like structure. The decay rates directly obtained by parametrizing the curves S2(tm,tp) with stretched exponential functions show Arrhenius behaviour pointing to an activation energy of approximately 0.5 eV. This value, probed by employing an atomic-scale NMR method, is in very good agreement with that deduced from impedance spectroscopy used to measure macroscopic Li transport parameters. Most likely, the two methods are sensitive to the same hopping correlation function although Li dynamics are probed in a quite different manner.