Regensburg 2010 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 6: Diffusion and Point Defects II
MM 6.4: Vortrag
Montag, 22. März 2010, 12:15–12:30, H6
Ultra-slow lithium diffusion in Li3NbO4 probed by 7 Li stimulated echo NMR spectroscopy — •Benjamin Ruprecht and Paul Heitjans — Institut für Physikalische Chemie und Elektrochemie, Leibniz Universität Hannover, D-30167 Hannover
Currently, a variety of fast Li conductors attract much attention due to possible future applications in batteries. In contrast, apart from fundamental aspects, for other applications such as breeder materials for fusion reactors materials with exceptionally slow Li transport are needed. We present studies on the ultra-slow Li transport in the model system Li3NbO4 (cubic, space group I-43m) by 7Li Spin-Alignment Echo Nuclear Magnetic Resonance (SAE NMR) spectroscopy [1]. NMR spectroscopy allows one to probe ionic transport on a microscopic scale. In Li3NbO4 the Li ions reside in different electrical field gradients at the nuclear sites giving rise to different quadrupolar precession frequencies ωQ. Diffusion induced changes of ωQ during the mixing time tm of the pulse sequence used lead to a decay of the stimulated echo observed. By recording the tm dependence of the echo amplitude the SAE NMR experiment yields two-time single-particle correlation functions and gives direct access to correlation rates τc−1 which may be identified with Li jump rates [2]. In the case of Li3NbO4 ultra-slow lithium jumps in the regime 1..104 s−1 (373..553 K) were found showing that Li3NbO4 is indeed a very poor lithium ion conductor.
1.5em -1.5em [1] R. Böhmer, K. R. Jeffrey, M. Vogel, Prog. Nucl. Magn. Reson. Spectrosc. 50 (2007) 87
[2] M. Wilkening, P. Heitjans, Solid State Ion. 177 (2006) 3031.