Ion transport and diffusion in nanocrystalline and glassy ceramics |
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Authors: | P Heitjans E Tobschall M Wilkening |
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Institution: | 1.Institute of Physical Chemistry and Electrochemistry, and Center for Solid State Chemistry and New Materials, Leibniz University Hannover,Hannover,Germany |
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Abstract: | In the present paper we review experimental studies on ion transport and diffusion in nanocrystalline and
glassy ceramics of LiNbO3 and LiAlSi2O6 and report on new ones on LiBO2 using the measurement of dc
conductivities and 7Li nuclear magnetic resonance spin-lattice relaxation rates. Nanocrystalline ceramics, with an
average particle size of 50 nm and less, often show an enhanced diffusivity compared to their microcrystalline
(μm-sized) counterparts. This increase is due to the large fraction of atoms or ions located in the interfacial
regions. A key for understanding the structure-mobility relations in nanocrystalline ceramics is to clarify the
microscopic structure of the grain boundaries and also the morphology of the grain boundary network. In this context
it is useful to study not only the ion transport properties of the nano- and microcrystalline materials but also those
of the corresponding glassy forms. Such comparative studies gave strong evidence that in some cases the interfacial
regions are of amorphous structure. For example, this was recently shown for nanocrystalline lithium niobate which was
prepared by high-energy ball milling. |
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