Lithium dynamics in the Li0.18La0.61TiO3 perovskite quenched from 1623K was analyzed by means of 7Li Nuclear magnetic resonance spectroscopy and neutron powder diffraction. The Rietveld analysis of the diffraction pattern showed rhombohedral symmetry with Li ions occupying square windows that connect contiguous A sites of the perovskite. The hopping of Li ions through these windows produces the line narrowing detected above 170K in 7Li nuclear magnetic resonance spectra. Deconvolution of nuclear magnetic resonance spectra showed the existence of two Li species that exchange their positions between 250 and 350K. In this temperature range, a plateau was detected in T2-1 plots, which was ascribed to the existence of 2-dimensional motions of Li in ordered domains of the perovskite. Evidence of this limited motion comes from the frequency dependence of the spin-lattice relaxation rates measured at the high-temperature side of the asymmetrical 1/T1 maximum. Other measurements indicated that there was a slower motion of Li, with a characteristic time of 3 x 10–6s, at room temperature; attributed to isotropic 3-dimensional diffusion.

Lithium Dynamics in the Fast Ionic Conductor Li0.18La0.61TiO3 Probed by 7Li NMR Spectroscopy. A.Rivera, J.Sanz: Physical Review B, 2004, 70[9], 094301 (7pp)