Atomic resolution imaging of cation ordering in niobium–tungsten complex oxides

AbstractEnergy dispersive X-ray emission imaging at atomic resolution is a powerful tool to solve order–disorder problems in complex metal oxide crystals, supplementing conventional X-ray or neutron diffraction. Here, we use this method, based on scanning transmission electron microscopy, to investigate cation ordering in ternary metal oxides 4Nb2O5·9WO3 and 2Nb2O5·7WO3, which have recently attracted attention as energy storage materials in lithium-ion batteries. Their crystal structures are a tetragonal tungsten bronze-type and its hybrid with a ReO3-type ‘block structure’, respectively. Our study reveals the presence of chemical ordering of metal ions in these materials, which have previously been assumed to be solid-solutions. In particular, we show that the two types of cations, Nb and W, are well ordered in their lattices, and that the Nb ions tend to occupy one third of the pentagonal channel sites. These results demonstrate that atomic resolution X-ray emission imaging is an effective alternative approach for the study of locally ordered crystal structures.

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Atomic-resolution STEM-EDS studies of cation ordering in Ti-Nb oxide crystals

Scientific Reports ◽

10.1038/s41598-021-97244-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Sumio Iijima ◽

Ichiro Ohnishi ◽

Zheng Liu

Keyword(s):

Electrode Materials ◽

Diffraction Method ◽

Atomic Resolution ◽

Energy Storage Materials ◽

Cation Ordering ◽

Chemical Ordering ◽

Scanning Transmission ◽

Battery Electrode ◽

Ternary Metal ◽

Oxide Crystals

AbstractTernary metal oxide compounds, such as Ti-Nb and Nb-W oxides, have renewed research interest in energy storage materials because these oxides contain multivalent metal ions that may be able to control the ion transport in solid lithium batteries. One of these oxides is Ti2Nb10O29, which is composed of metal–oxygen octahedra connected through corner-sharing and edge-sharing to form “block structures”. In the early 1970s Von Dreele and Cheetham proposed a metal-atoms ordering in this oxide crystal using Rietveld refined neutron powder diffraction method. Most recent studies on these oxides, however, have not considered cation ordering in evaluating the battery electrode materials. In this paper, by utilizing the latest scanning transmission electron microscopy combined with energy dispersive X-ray spectroscopy imaging technology, the cation chemical ordering in those oxide crystals was directly revealed at atomic resolution.

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Intergrowth of niobium tungsten oxides of the tetragonal tungsten bronze type

Zeitschrift für Naturforschung B ◽

10.1515/znb-2020-0107 ◽

2020 ◽

Vol 75 (11) ◽

pp. 913-919

Author(s):

Frank Krumeich

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Tungsten Bronze ◽

Structural Complexity ◽

Dark Field ◽

Tetragonal Tungsten Bronze ◽

Tungsten Oxides ◽

Transmission Electron ◽

Scanning Transmission

AbstractSince the 1970s, high-resolution transmission electron microscopy (HRTEM) is well established as the most appropriate method to explore the structural complexity of niobium tungsten oxides. Today, scanning transmission electron microscopy (STEM) represents an important alternative for performing the structural characterization of such oxides. STEM images recorded with a high-angle annular dark field (HAADF) detector provide not only information about the cation positions but also about the distribution of niobium and tungsten as the intensity is directly correlated to the local scattering potential. The applicability of this method is demonstrated here for the characterization of the real structure of Nb7W10O47.5. This sample contains well-ordered domains of Nb8W9O47 and Nb4W7O31 besides little ordered areas according to HRTEM results. Structural models for Nb4W7O31 and twinning occurring in this phase have been derived from the interpretation of HAADF-STEM images. A remarkable grain boundary between well-ordered domains of Nb4W7O31 and Nb8W9O47 has been found that contains one-dimensionally periodic features. Furthermore, short-range order observed in less ordered areas could be attributed to an intimate intergrowth of small sections of different tetragonal tungsten bronze (TTB) based structures.

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Incommensurate modulation of calcium barium niobate (CBN28 and Ce:CBN28)

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768111054863 ◽

2012 ◽

Vol 68 (2) ◽

pp. 101-106 ◽

Cited By ~ 15

Author(s):

Heribert A. Graetsch ◽

Chandra Shekhar Pandey ◽

Jürgen Schreuer ◽

Manfred Burianek ◽

Manfred Mühlberg

Keyword(s):

Crystal Structures ◽

Tungsten Bronze ◽

Atomic Displacement ◽

Type Structure ◽

Formula Unit ◽

Tetragonal Tungsten Bronze ◽

First Order ◽

Oxygen Coordination ◽

Incommensurate Modulation ◽

Atomic Displacement Parameters

The incommensurately modulated crystal structures of Ca0.28Ba0.72Nb2O6 (CBN28) and Ce0.02Ca0.25Ba0.72Nb2O6 (Ce:CBN28) were refined in the supercentred setting X4bm(AA0,−AA0) of the 3 + 2-dimensional superspace group P4bm(aa½,−aa½). Both compounds are isostructural with a tetragonal tungsten bronze-type structure. The modulation of CBN28 consists of a wavy distribution of Ba and Ca atoms as well as vacancies on the incompletely occupied Me2 site with 15-fold oxygen coordination. The occupational modulation is coupled with a modulation of the atomic displacement parameters and a very weak modulation of the positional parameters of Me2. The surrounding O atoms show strong displacive modulations with amplitudes up to ca 0.2 Å owing to the cooperative tilting of the rigid NbO6 octahedra. The Me1 site with 12-fold coordination and Nb atoms are hardly affected by the modulations. Only first-order satellites were observed and the modulations are described by first-order harmonics. In Ce:CBN28 cerium appears to be located on both the Me2 and Me1 sites. Wavevectors and structural modulations are only weakly modified upon substitutional incorporation of 0.02 cerium per formula unit of calcium.

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Absolute-Scale Comparison with Simulation for Quantitative Energy-Dispersive X-Ray Spectroscopy in Atomic-Resolution Scanning Transmission Electron Microscopy

Microscopy and Microanalysis ◽

10.1017/s1431927617002628 ◽

2017 ◽

Vol 23 (S1) ◽

pp. 388-389 ◽

Cited By ~ 1

Author(s):

S.D. Findlay ◽

Z. Chen ◽

M. Weyland ◽

X. Sang ◽

W. Xu ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Scanning Transmission Electron Microscopy ◽

Energy Dispersive ◽

Atomic Resolution ◽

X Ray ◽

Scanning Transmission Electron ◽

Absolute Scale ◽

Transmission Electron ◽

Scanning Transmission

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Phosphate tungsten bronze series: crystallographic and structural properties of low-dimensional conductors

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768101009685 ◽

2001 ◽

Vol 57 (5) ◽

pp. 603-632 ◽

Cited By ~ 32

Author(s):

P. Roussel ◽

O. Pérez ◽

Ph. Labbé

Keyword(s):

Crystal Structures ◽

Structural Properties ◽

Tungsten Bronze ◽

Structural Description ◽

X Ray ◽

X Ray Scattering ◽

Modulated Structures ◽

Low Dimensionality ◽

Low Dimensional ◽

Thickness Function

Phosphate tungsten bronzes have been shown to be conductors of low dimensionality. A review of the crystallographic and structural properties of this huge series of compounds is given here, corresponding to the present knowledge of the different X-ray studies and electron microscopy investigations. Three main families are described, monophosphate tungsten bronzes, Ax (PO2)4(WO3)2m , either with pentagonal tunnels (MPTBp) or with hexagonal tunnels (MPTBh), and diphosphate tungsten bronzes, Ax (P2O4)2(WO3)2m , mainly with hexagonal tunnels (DPTBh). The general aspect of these crystal structures may be described as a building of polyhedra sharing oxygen corners made of regular stacking of WO3-type slabs with a thickness function of m, joined by slices of tetrahedral PO4 phosphate or P2O7 diphosphate groups. The relations of the different slabs with respect to the basic perovskite structure are mentioned. The structural description is focused on the tilt phenomenon of the WO6 octahedra inside a slab of WO3-type. In this respect, a comparison with the different phases of the WO3 crystal structures is established. The various modes of tilting and the different possible connections between two adjacent WO3-type slabs involve a great variety of structures with different symmetries, as well as the existence of numerous twins in MPTBp's. Several phase transitions, with the appearance of diffuse scattering and modulation phenomena, were analysed by X-ray scattering measurements and through the temperature dependence of various physical properties for the MPTBp's. The role of the W displacements within the WO3-type slabs, in two modulated structures (m = 4 and m = 10), already solved, is discussed. Finally, the complexity of the structural aspects of DPTBh's is explained on the basis of the average structures which are the only ones solved.

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A Study of Grain Boundaries in High TC Superconducting Yba2Cu3O7-x Thin Films Using High Resolution Analytical Stem

MRS Proceedings ◽

10.1557/proc-169-773 ◽

1989 ◽

Vol 169 ◽

Author(s):

D. H. Shin ◽

J. Silcox ◽

S. E. Russek ◽

D. K. Lathrop ◽

R. A. Buhrman

Keyword(s):

Thin Films ◽

High Resolution ◽

Grain Boundaries ◽

Scanning Transmission Electron Microscope ◽

Atomic Resolution ◽

High Tc ◽

X Ray ◽

Transmission Electron ◽

Scanning Transmission ◽

Edx Microanalysis

AbstractGrain boundaries in thin films of high Tc YBa2Cu3O7-x superconductors have been investigated with high resolution scanning transmission electron microscope (STEM) imaging and nanoprobe energy dispersive x-ray (EDX) analysis. Atomic resolution images indicate that the grain boundaries are mostly clean, i.e., free of a boundary layer of different phase or of segregation, and are often coherent. EDX microanalysis with a 10 Å spatial resolution also indicates no composition deviation at the grain boundaries.

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Composition measurement in substitutionally disordered materials by atomic resolution energy dispersive X-ray spectroscopy in scanning transmission electron microscopy

Ultramicroscopy ◽

10.1016/j.ultramic.2016.10.006 ◽

2017 ◽

Vol 176 ◽

pp. 52-62 ◽

Cited By ~ 9

Author(s):

Z. Chen ◽

D.J. Taplin ◽

M. Weyland ◽

L.J. Allen ◽

S.D. Findlay

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Scanning Transmission Electron Microscopy ◽

Energy Dispersive ◽

Atomic Resolution ◽

Disordered Materials ◽

X Ray ◽

Transmission Electron ◽

Scanning Transmission ◽

Composition Measurement

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Unified approach for determining tetragonal tungsten bronze crystal structures

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314003994 ◽

2014 ◽

Vol 70 (3) ◽

pp. 283-290 ◽

Cited By ~ 7

Author(s):

M. Smirnov ◽

P. Saint-Grégoire

Keyword(s):

Experimental Data ◽

Crystal Structures ◽

Tungsten Bronze ◽

Unified Approach ◽

Tetragonal Tungsten Bronze ◽

Theoretical Predictions ◽

Rigid Unit Modes

Tetragonal tungsten bronze (TTB) oxides are one of the most important classes of ferroelectrics. Many of these framework structures undergo ferroelastic transformations related to octahedron tilting deformations. Such tilting deformations are closely related to the rigid unit modes (RUMs). This paper discusses the whole set of RUMs in an ideal TTB lattice and possible crystal structures which can emerge owing to the condensation of some of them. Analysis of available experimental data for the TTB-like niobates lends credence to the obtained theoretical predictions.

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