NMR and Impedance Spectroscopy Studies on Lithium Ion Diffusion in Microcrystalline γ-LiAlO2

In this work nuclear magnetic resonance (NMR) and impedance spectroscopy (IS) studies on Li ion dynamics in microcrystalline gamma-LiAlO2 are presented. The sample was prepared by solid state synthesis between Li2CO3 and Al2O3 in air, followed by a quenching procedure. The presence of phase-pure gamma-LiAlO2 was confirmed by X-ray powder diffraction including Rietveld refinement. Further structural characterization was done with Li-6, Li-7 and Al-27 NMR. Several NMR techniques such as spin-lattice relaxation measurements, motional narrowing experiments, as well as spin-alignment echo were employed for the investigation of Li ion diffusion. The measurements were carried out at high temperatures (up to 970 K) in order to access the regime of Li ion motion being very slow. The dc conductivities measured by IS in the temperature range from 680 K to 870 K were converted to diffusion coefficients being compatible with those obtained by NMR.