Structure and dynamics in nanoionic materials

Abstract

Nanomaterials, materials with particle dimensions less than 100 nm, show a range of unusual properties when compared with their bulk counterparts. Atomic transport is one of these properties and nanomaterials have been reported as having exceptionally high diffusion coefficients. In the case of ionic materials the atomic transport is important in a number of technological applications where they are used as solid electrolytes, for example in sensors, batteries and fuel cells. Hence ionic nanomaterials often referred to as nanoionics, can offer the means of producing electrolytes with improved performance. This contribution will examine the mechanisms of atomic transport in nanoionics in two model materials, zirconia and lithium niobate. Since an understanding of these mechanisms is dependent on knowledge of the microstructure of the materials consideration will also be given to the structural characterisation of the materials, with a focus on X-ray absorption spectroscopy. The use of this technique to characterise mesoporous a-Fe 2 O 3 is also discussed.

EXAFS study of nanocrystalline CeO2 samples prepared by sol–gel and ball-milling routes

“…Since they were only heated at 600 • C, they may still contain some amorphous material that is not detected by XRD analysis. This has been shown previously in the case of sol-gel prepared nanocrystalline ZrO 2 , where annealing at temperatures above 600 • C was required to fully crystallise the material [13], while low temperature (17 K) EXAFS spectra have shown that there is no reduction in amplitude for well crystallised 10 nm tetragonal ZrO 2 compared with bulk tetragonal ZrO 2 [14]. However, the ball-milled sample shows a greater reduction in the amplitude of the Fourier transform, than the Al 2 O 3 -pinned CeO 2 even though the particle sizes are similar.…”

Mismatch in cation size causes rapid anion dynamics in solid electrolytes: the role of the Arrhenius pre-factor

“…Nanostructured materials play a prominent role in these fields. 1,5,6 Although ion dynamics in a huge number of various nanomaterials have been studied over the last decades with a wide range of techniques, [7][8][9][10][11] our picture about ionic diffusivity is far from being completely understood. The introduction of defects, that is, in a more general sense describable with structural disorder, represents a powerful instrument with which we can control the chemical and physical properties of a material.…”

Atomic-scale measurement of ultraslow Li motions in glassyLiAlSi2O6by two-timeL6Wilkening1, Kuhn2, Heitjans3 2008Phys. Rev. B594500View full textAdd to dashboardCite

“…This is due to the often found observation that structurally disordered Li conductors exhibit exceptionally fast ionic diffusivity as compared to their low-defective crystalline counterparts. [9][10][11][12][13][14] Understanding the basics of transport phenomena in such materials in more detail is indispensable in effective battery research. In this context, it will be useful to study Li diffusion over a preferably large dynamic range, i.e., including also extremely slow cation motions.…”