A novel intergrowth structure between ReO3-type and tetragonal tungsten bronze-type in the Zr/Nb/W/O system

The intergrowth structure of a zirconium niobium tungsten oxide has been determined by transmission electron microscopy methods. Electron diffraction patterns reveal the parameters of the monoclinic lattice: a = 19.0, b = 3.9 and c = 13.8 Å; β = 93.5°. Additional reflections in higher-order Laue zones indicate the presence of a diagonal glide plane, leading to a larger unit cell. A structure model of composition Zr n Nb8−2n W12+n O56 (0.5 < n < 1) has been derived from high-resolution lattice images. Alternating slabs of ReO3-type and of tetragonal tungsten bronze structure are intergrown coherently. Two five-membered rings of MO6 octahedra belonging to adjacent tetragonal tungsten bronze subcells are connected by having two octahedra in common. For the first time, this arrangement of double pentagons is observed in a regular structure.

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Transmission electron microscopy evidence of a new tetragonal tungsten bronze superstructure

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1524/zkri.1997.212.10.708 ◽

1997 ◽

Vol 212 (10) ◽

Cited By ~ 1

Author(s):

F. Krumeich

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Electron Diffraction ◽

Tungsten Bronze ◽

Tetragonal Tungsten Bronze ◽

Transmission Electron ◽

Diffraction Patterns

AbstractElectron diffraction patterns of M

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Order and Disorder in Niobium Tungsten Oxides of the Tetragonal Tungsten Bronze Type

Acta Crystallographica Section B Structural Science ◽

10.1107/s010876819701971x ◽

1998 ◽

Vol 54 (3) ◽

pp. 240-249 ◽

Cited By ~ 11

Author(s):

F. Krumeich

Keyword(s):

Diffuse Scattering ◽

Tungsten Bronze ◽

Oxidation Products ◽

Tetragonal Tungsten Bronze ◽

Tungsten Oxides ◽

Order And Disorder ◽

Transmission Electron ◽

Diffraction Patterns ◽

The Stability ◽

Microscopy Images

Two superstructures of the TTB type (tetragonal tungsten bronze) exist in the system Nb2O5/WO3. They are caused by an ordered arrangement of pentagonal tunnels filled with metal–oxygen strings. Besides the well known 4:9 phase (Nb8W9O47), which has a tripled b axis, evidence for a new orthorhombic structure, Nb6W8O39 (a = b = 27.3 Å), has been found. The oxidation products of Nb7W10O47 and Nb4W13O47 frequently comprise less-ordered arrangements of filled tunnels, causing diffuse scattering. In Nb7W10O47.5 the electron diffraction patterns (along [001]) of many crystal fragments show circular diffuse scattering, which appears around the main reflections of the TTB substructure with two distinct radii (r*). r* \simeq 0.33a* indicates the predominance of 4:9-type domains, whereas r* \simeq 0.41a* corresponds to Nb6W8O39. In Nb4W13O49 the diffuse scattering pattern is cross-shaped; this is due to the presence of long slabs of diamond-linked pentagonal columns. Structure models for these particular states of order have been derived from high-resolution transmission electron microscopy images. Some general principles for the formation of the different arrangements are deduced. Apparently, two distinct types of link between the filled pentagonal tunnels are important features which lead to the stability of these structures.

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Processing Effects on the Microstructure of Sol-Gel Derived SBN Thin Films

MRS Proceedings ◽

10.1557/proc-346-297 ◽

1994 ◽

Vol 346 ◽

Cited By ~ 1

Author(s):

L.A. Momoda ◽

M.C. Gust ◽

M.L. Mecartney

Keyword(s):

Thin Films ◽

Sol Gel ◽

Tungsten Bronze ◽

Treatment Schedule ◽

Size Distributions ◽

Tungsten Bronze Structure ◽

Tetragonal Tungsten Bronze ◽

Transmission Electron ◽

Processing Effects ◽

Hydrolysis Conditions

ABSTRACTMicrostructural changes in sol-gel derived SrxBa1-xNb2O6 (SBN) thin films were monitored as a function of chemical variations in the precursor sol and of processing variations of the thin films. 6000À Sr0.5Ba0.5Nb2O6 thin films were deposited from different alkoxide based precursors under various hydrolysis conditions. The tetragonal tungsten bronze structure was achieved in films at temperatures on the order of 700°C. Preferential (001) orientation of the tetragonal lattice was found to be very dependent upon the substrate orientation as well as thermal treatment schedule. Transmission electron microscopy (TEM) was used to examine the film microstructure. Orientational effects were verified by TEM as well as a tendency for a porous structure in the alkoxide derived films. Substrate and processing dependent grain size and size distributions were also noted.

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A Novel TEM Technique for Characterizing As-Grown CVD Diamond Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089093 ◽

1991 ◽

Vol 49 ◽

pp. 956-957 ◽

Cited By ~ 1

Author(s):

Z.L. Wang ◽

J. Bentley ◽

R.E. Clausing ◽

L. Heatherly ◽

L.L. Horton

Keyword(s):

Diamond Films ◽

Chemical Vapor ◽

Growth Direction ◽

Dark Field ◽

Growth Surface ◽

Specimen Preparation ◽

Transmission Electron ◽

Diffraction Patterns ◽

First Time ◽

Microstructural Studies

Microstructural studies by transmission electron microscopy (TEM) of diamond films grown by chemical vapor deposition (CVD) usually involve tedious specimen preparation. This process has been avoided with a technique that is described in this paper. For the first time, thick as-grown diamond films have been examined directly in a conventional TEM without thinning. With this technique, the important microstructures near the growth surface have been characterized. An as-grown diamond film was fractured on a plane containing the growth direction. It took about 5 min to prepare a sample. For TEM examination, the film was tilted about 30-45° (see Fig. 1). Microstructures of the diamond grains on the top edge of the growth face can be characterized directly by transmitted electron bright-field (BF) and dark-field (DF) images and diffraction patterns.

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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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