Regensburg 2010 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 6: Diffusion and Point Defects II

MM 6.4: Talk

Monday, March 22, 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 ω_Q. Diffusion induced changes of ω_Q during the mixing time t_m of the pulse sequence used lead to a decay of the stimulated echo observed. By recording the t_m dependence of the echo amplitude the SAE NMR experiment yields two-time single-particle correlation functions and gives direct access to correlation rates τ_c⁻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.