The Crystal Structure of Nb16W18O94, a Member of a (MeO)xMeO3 Family of Compounds.

Sleight, A.W.; Sletten, Einar; Sletten, Jorunn; Kulonen, E.; Brunvoll, J.; Bunnenberg, E.; Djerassi, Carl; Records, Ruth

doi:10.3891/acta.chem.scand.20-1102

Cited by 95 publications

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“…They are therefore oxygen deficient with respect to WOa, and are undoubtedly a consequence of the reaction with Nb2Os. The size of the elements of similar structure which occurs in 4Nb2Os.9WO3, is 1.09 × 1.12 nm, as determined from the atomic coor- dinates given by Sleight (1966). This agrees closely with the size of the ReOa-type element in Fig.…”

Section: Ttb Elements In a Reo3-type Matrixsupporting

confidence: 83%

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: Ttb Elements In a Reo3-type Matrixsupporting

confidence: 83%

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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“…Calculations were also carried out for Nba6W18094 assuming a structure determined by Sleight (1966). Fig.…”

Section: (E-e°)2-]mentioning

confidence: 99%

Approximations for the calculation of high-resolution electron-microscope images of thin films

Fejes¹

1977

Acta Cryst A

110

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“…The occupation of the pentagonal tunnels, similar to the observation mentioned above, was reported in some ordered structures such as 4Nb205. 9WO 3 (Sleight, 1966) and 2Nb2Os.TWO a (Iijima & Allpress, 1974a). The metal/oxygen ratio in the region of the elements of the TTB type with two pentagonal tunnels occupied becomes MO2.~3 ~, compared with MO 3 for the ReO 3 type.…”

Section: Methodsmentioning

confidence: 99%

Structural studies by high-resolution electron microscopy: intergrowth of ReO₃ and tetragonal tungsten bronze-type structures in the system Nb₂O₅–WO₃

Iijama¹

1978

Acta Cryst Sect A

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With high-resolution electron microscopy new crystal structures were found in the binary system of Nb205-WO 3 oxides. The compounds are proposed to have the mole ratios 4Nb205. 22WO 3 and 4Nb205. 50WO 3. The crystal structures are ascribed to intimate intergrowths of two known structures, the ReO 3 type and tetragonal tungsten bronze type. The latter grows coherently in the host lattice of the former, forming regularly arranged slabs. The coherent intergrowth of the tetragonal tungsten bronze structures is described as the 'rotation operation' on the ReO3-type structure. IntroductionCompounds in the binary system of Nb205-WO3 oxides have been intensively studied. According to the studies on the phase diagram of this system by Roth & Wadsley (1965), the compounds are grouped into three different structure types: the 'block structures' occurring in the composition range of O/M (oxygen/metal ratio) = 2.50-2-66, the 'Magn~li phases' in the WO 3-rich region of O/M = 2.90-3.00, and in the range of O/M = 2.66-2.90 the tetragonal tungsten bronze-type structure (hereinafter abbreviated TTB type). For the TTB type, two ordered structures 4Nb205. 9WO 3 and 2Nb205. 7WO 3 were found. The block structures and the Magn61i phases having the ReO 3 type as a basic structure contain the crystallographic shear structures as a common structural component where the individual metal-oxygen octahedra are linked with their neighboring octahedra by edge sharing instead of corner sharing in the basic structure of the ReO 3 type. In the Magn61i phases the crystallographic shear planes are arranged one-dimensionally, forming slabs of the ReO 3 type, while in the block structures the crystallographic shear planes are arranged two-dimensionally, forming columns of the ReO 3 type. A slight change in composition results in rearrangement of the crystallographic shear planes and thus a slightly different structure from one compound to another, so that a homologous series of the compounds is formed (Wadsley & Andersson, 1970).The structure of 2Nb2Os.7WO3 was determined from the study of the high-resolution electron micrographs of crystals having a nominal composition of 19Nb2Os.63WO~ (lijima & Allpress, 1974a) and was found to result from an intergrowth of the two different structures of ReO 3 type and the TTB type. It was proposed that since the small domains of the ReO3-type structure are intergrown coherently with the TTB type in 2Nb205. 7WO 3, a transformation of this structure from the ReO 3 type to the TI'B type, which occurs in solid-state reactions, would be conceivable by a periodic application of the rotation of the groups of the corner-shared octahedra to the ReO 3 type. Direct evidence of the rotation which causes formation of single elements of the TTB-type structure in some regions of the ReO 3 type has been demonstrated by Iijima & Allpress (1974b). This was observed often in disordered regions of crystals having a nominal composition of 19Nb2Os.63WO 3. More general considerations on structural relations between the ReO 3 type and ...

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The Crystal Structure of Nb16W18O94, a Member of a (MeO)xMeO3 Family of Compounds.

Cited by 95 publications

References 0 publications

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

Approximations for the calculation of high-resolution electron-microscope images of thin films

Structural studies by high-resolution electron microscopy: intergrowth of ReO₃ and tetragonal tungsten bronze-type structures in the system Nb₂O₅–WO₃

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The Crystal Structure of Nb16W18O94, a Member of a (MeO)xMeO3 Family of Compounds.

Cited by 95 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

Approximations for the calculation of high-resolution electron-microscope images of thin films

Structural studies by high-resolution electron microscopy: intergrowth of ReO3 and tetragonal tungsten bronze-type structures in the system Nb2O5–WO3

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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

Structural studies by high-resolution electron microscopy: intergrowth of ReO₃ and tetragonal tungsten bronze-type structures in the system Nb₂O₅–WO₃