Paper No. 5-2
Presentation Time: 8:20 AM
ATOMIC RESOLUTION EDS-STEM MICROSCOPY OF NANO-STRUCTURED MATERIALS (Invited Presentation)
Recently Ti-Nb-W oxides with complex crystal structures attract many researchers because of their possible candidate for all-solid Lithium battery electrodes. . One of the ternary oxides of Ti and Nb has been thought to form a solid-solution crystal because their ion radii are similar. The crystal structures of these oxides were mostly studies by X-ray or neutron diffraction methods [2,3] and complementally by a high resolution transmission electron microscopy (HRTEM) method. However the method has been limited to solve problems with order disorder structures. This limitation has been overcome by recent development in STEM (Scanning TEM) combined with the advanced EDS (Energy Dispersive X-ray Spectroscopy) technology. The spatial resolution of EDS has allowed to image individual columns of atoms in a crystal, or elemental mapping of a crystal including oxygen atoms. Here we report, as an example, a clear evidence of cations ordering in a ternary metal oxide crystal of Ti2Nb10O29 and other related oxides that have been intensively studied by the present author in the 1970s [4,5].
- K. J. Griffith, K. M. Wiaderek, G. Cibin, L. E. Marbella & C. P. Grey. “Niobium tungsten oxides for high-rate lithium-ion energy storage”, Nature, 556, 559-563 (2018).
- A. D. Wadsley, “Mixed Oxides of Titanium and Niobium. II. The crystal structures of the dimorphic forms of Ti2Nb10O29” Acta Cryst. 14, 664-670 (1961).
- R. B. Von Dreele and A. K. Cheetham, Proc. R. Soc. Lond. “The structures of some titanium-niobium oxides by powder neutron diffraction”, A. 338, 311-326 (1974).
- S. Iijima, “High-Resolution electron microscopy of crystal lattice of titanium-niobium oxides” JAP, 42, 5891-5893 (1971).
- S. Iijima, S. Kimura and M. Goto, “Direct observation of point defects in Nb12O29 by high-resolution electron microscopy” Acta Cryst. A29, 632-636 (1973).