The Crystal Structure of Nb2WO8.

Lundberg, Monica; Lundeland, Magne; Marøy, Kjartan; Tricker, M. J.; Svensson, Sigfrid

doi:10.3891/acta.chem.scand.26-2932

Cited by 46 publications

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“…As the WO3 content of the product increases, so will the size of the component blocks, until finally the NbzOs-type of structure loses stability, and transformation to WNbzOs occurs. The structure of the latter (Lundberg, 1972) is closely related to that of LiNb6OlsF (Lundberg, 1965), which as Hyde & O'Keeffe (1973) have shown, can be readily derived from the ReOs structure by the periodic application of the rotation operation illustrated in Fig. 6.…”

Section: The Reaction Mechanismmentioning

confidence: 78%

Structural studies by electron microscopy: coherent intergrowth of the ReO₃and tetragonal tungsten bronze structure types in the system Nb₂O₅–WO₃

Iijima¹,

Allpress²

1974

Acta Cryst Sect A

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is a strong tendency for what might be called microstructural order; i.e. once a configuration of domains is established during the reaction, the boundaries between them will tend to take up directions and structures in which the discrepancies of phase and/or composition are accommodated with the maximum possible degree of local order. The elimination of all these boundaries will inevitably require very much more extensive migration of the contents of occupied tunnels, either via interstitial sites, or involving exchange with sites in the host lattice. In the case of 2Nb205.7WOa, this migration will be accompanied by the reorientation of elements of the host lattice, in order to produce the required arrangement of 4 × 4 ReO3-type blocks. In view of these extensive movements, and the relatively weak long-range forces between occupied tunnels, these processes are likely to be slow, and it is therefore not surprising that large numbers of fault boundaries have been observed, particularly in 2Nb2Os.7WO3. These conclusions could probably be verified by examination of a series of specimens heat-treated for varying periods of time and/or varying temperature to demonstrate the method of approach to equilibrium. High-resolution lattice images from WO3-rich compositions in the system Nb2Os-WO3 contain direct evidence for the coherent intergrowth of extensive domains of several orientations of the ReO3-type structure with the more complex tetragonal tungsten bronze-type structure. A model for the transformation between the two structure types is proposed.

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Section: The Reaction Mechanismmentioning

confidence: 78%

Structural studies by electron microscopy: coherent intergrowth of the ReO₃and tetragonal tungsten bronze structure types in the system Nb₂O₅–WO₃

Iijima¹,

Allpress²

1974

Acta Cryst Sect A

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“…All M atoms are displaced from z = 0, just as in Nb2WO 8 (Lundberg, 1972). On the other hand, the O atoms are less than 3a from z = 0 or z = ½ (see Table 1).…”

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confidence: 99%

“…From high-resolution electron-microscopy (HREM) images recorded with the Siemens microscope it was inferred that the title compound contains structural elements of the type found in LiNb60~5 F (Lundberg, 1965), Nb2WO s (Lundberg, 1972) and NaNb60~5 F (Andersson, 1965). This assumption was supported by the fact that the b axis is, within less than 1%, equal to twice the distance between two pentagonal columns (PC's) joined via a triangular link in these three compounds (for nomenclature see Lundberg, Sundberg & Magn~li, 1982).…”

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confidence: 99%

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Na7Nb15W13O80 – A new type of tunnel structure studied by X-ray diffraction and HREM techniques

Marinder¹,

Sundberg²

1984

Acta Crystallogr C

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Abstract. orthorhombic, Pmab, a= 21.962 (2), b = 17.763 (2), c= 3.9165 (3),/k, V---1527.9 (3) A 3, Z= 1, Din= 5.61 (1), Dx= 5.664 (1) g cm -3, 2(Mo Ka) = 0.7107 ,/~, /t(Mo Ka) = 241 cm -l, F(000) = 2292.7, T= 293 K, R = 0.058 for 936 independent reflexions. The structure is built up of pentagonal columns connected to each other directly and via a string of MO 6 octahedra, running parallel to the c axis. Large tunnels with an S-shaped cross section are formed, in which the Na atoms are statistically distributed. Four of the five heavy-atom sites are randomly occupied by Nb and W; the fifth entirely by Nb. X-ray and electron diffraction experiments indicate that the K and Ag analogues are isostructural. HREM images of the K compound confirm the structure.

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“…Since PTs and PCs can be arranged in many ways, preparations of this type are typically disordered (14}16). However, at certain compositions ordered structures exist, such as Nb W O (17), Nb W O (18,19), and Nb WO (20). Of these only Nb W O (henceforth referred to as 3-TTB) is based entirely on a TTB framework, possessing a simple three-fold superstructure where 4 out of 12 empty PTs are "lled to produce PCs, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Quaternary Lead–Niobium–Tungsten Oxides Based on the Tetragonal Tungsten Bronze Structure

Haydon

Jefferson

2001

Journal of Solid State Chemistry

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The Crystal Structure of Nb2WO8.

Cited by 46 publications

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Structural studies by electron microscopy: coherent intergrowth of the ReO₃and tetragonal tungsten bronze structure types in the system Nb₂O₅–WO₃

Structural studies by electron microscopy: coherent intergrowth of the ReO₃and tetragonal tungsten bronze structure types in the system Nb₂O₅–WO₃

Na7Nb15W13O80 – A new type of tunnel structure studied by X-ray diffraction and HREM techniques

Quaternary Lead–Niobium–Tungsten Oxides Based on the Tetragonal Tungsten Bronze Structure

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The Crystal Structure of Nb2WO8.

Cited by 46 publications

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Structural studies by electron microscopy: coherent intergrowth of the ReO3and tetragonal tungsten bronze structure types in the system Nb2O5–WO3

Structural studies by electron microscopy: coherent intergrowth of the ReO3and tetragonal tungsten bronze structure types in the system Nb2O5–WO3

Na7Nb15W13O80 – A new type of tunnel structure studied by X-ray diffraction and HREM techniques

Quaternary Lead–Niobium–Tungsten Oxides Based on the Tetragonal Tungsten Bronze Structure

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Structural studies by electron microscopy: coherent intergrowth of the ReO₃and tetragonal tungsten bronze structure types in the system Nb₂O₅–WO₃

Structural studies by electron microscopy: coherent intergrowth of the ReO₃and tetragonal tungsten bronze structure types in the system Nb₂O₅–WO₃