Lithium ionic jump motion in the fast solid ion conductor Li5La3Nb2O12

Using Li-7 NMR line-shape analysis, spin-lattice relaxation measurements and stimulated-echo spectroscopy, we investigate the lithium ionic jump motion in the garnet Li5La3Nb2O12. Results for two samples are compared, which were annealed at 850 degrees C (GR-850) and at 900 degrees C (GR-900), respectively. All Li-7 NMR data consistently show that two lithium species with distinguishable dynamical behaviors coexist in each of the samples. While the less mobile species is the majority component in GR-850, the more mobile species is the majority component in GR-900. Li-7 NMR stimulated-echo spectroscopy provides straightforward access to the correlation functions describing the jumps of the respective majority component in both samples. From the temperature-dependent correlation times, we obtain activation energies of 56 and 32 kJ mol(-1) for GR-850 and GR-900, respectively. For both samples, the correlation functions substantially deviate from simple exponential behavior, indicating a high complexity of the lithium ionic motion in Li5La3Nb2O12. (C) 2008 Elsevier Inc. All rights reserved.