Berlin 2008 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 9: Poster
DF 9.1: Poster
Dienstag, 26. Februar 2008, 15:00–18:00, Poster G
Tuning the Li diffusivity of poor ionic conductors by mechanical treatment: High Li conductivity of nanocrystalline LiTaO3 — •Viktor Epp, Martin Wilkening, Armin Feldhoff, and Paul Heitjans — Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstr. 3-3a, 30167 Hannover
Lithium tantalate, LiTaO3, with an average particle size in the µm range is known as a very poor Li ion conductor. It is shown that its Li conductivity can be drastically increased by ball-milling. The thus obtained nanostructured powder with an average particle size of about 20 nm shows a dc conductivity, σdc, of about 3·10−6 S cm−1 at T=450 K (σdcT=1.4·10−3 S cm−1 K) which is about five orders of magnitude larger than that of the corresponding microcrystalline powder at the same temperature. The activation energy EA is reduced by about one third, i. e., it decreases from EA=0.90(1) eV to about EA=0.63(1) eV. Similar results were previously obtained for lithium niobate [1]. The effect of different milling times on the ionic conductivity is studied. Furthermore, the thermal stability of the nanocrystalline materials against grain growth has been checked by in situ impedance spectroscopy. Interestingly, the Li conductivity of a sample milled for 16 h does not change much even when the material is exposed to about 700 K for several hours. Moreover, the Li self-diffusion in the nanostructured as well as the coarse grained materials is elucidated by various solid-state 7Li NMR techniques.
[1] P. Heitjans, M. Masoud, A. Feldhoff, M. Wilkening, Faraday Discuss. 134 (2007) 67.