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Title
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A pseudo-tetragonal tungsten bronze superstructure : a combined solution of the crystal structure of with advanced transmission electron microscopy and neutron diffraction
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Author
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Abstract
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| The crystal structure of the K6.4Nb28.2Ta8.1O94 pseudo-tetragonal tungsten bronze-type oxide was determined using a combination of X-ray powder diffraction, neutron diffraction and transmission electron microscopy techniques, including electron diffraction, high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), annular bright field STEM (ABF-STEM) and energy-dispersive X-ray compositional mapping (STEM-EDX). The compound crystallizes in the space group Pbam with unit cell parameters a = 37.468(9) Å, b = 12.493(3) Å, c = 3.95333(15) Å. The structure consists of corner sharing (Nb,Ta)O6 octahedra forming trigonal, tetragonal and pentagonal tunnels. All tetragonal tunnels are occupied by K+ ions, while 1/3 of the pentagonal tunnels are preferentially occupied by Nb5+/Ta5+ and 2/3 are occupied by K+ in a regular pattern. A fractional substitution of K+ in the pentagonal tunnels by Nb5+/Ta5+ is suggested by the analysis of the HAADF-STEM images. In contrast to similar structures, such as K2Nb8O21, also parts of the trigonal tunnels are fractionally occupied by K+ cations. |
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Language
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English
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Source (journal)
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Dalton Transactions : an international journal of inorganic chemistry / Royal Society of Chemistry [London] - Cambridge, 2003, currens
Journal of the Chemical Society : Dalton transactions. - London, 1972 - 1999
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Publication
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Cambridge
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Royal Society of Chemistry
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2016
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ISSN
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1477-9226
[print]
1477-9234
[online]
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DOI
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10.1039/C5DT03479E
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Volume/pages
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45
:3
(2016)
, p. 973-979
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ISI
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000367614700018
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Full text (Publisher's DOI)
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Full text (publisher's version - intranet only)
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