The structure of tantalum tungsten oxide Ta{sub 8}W{sub 9}O{sub 47}

Journal Article · Sat Jun 01 04:00:00 EDT 1996 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1996.0207· OSTI ID:390900

Krumeich, F; Geipel, T ^[1]

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1. Universitaet Bonn, Roemerstrasse (Germany)

The TTB-type (tetragonal tungsten bronze) structure of Ta{sub 8}W{sub 9}O{sub 47} has been investigated for two different processing temperatures (T = 1200 and 1400{degrees}C) using X-ray powder diffraction and TEM methods. The Guinier patterns for both temperatures show the reflections of the TTB-type structure. Additionally, the product obtained at 1400{degrees}C exhibits the reflections of a threefold TTB-type superstructure. HRTEM images of this specimen (along [001]) show that the superstructure originates from a systematic arrangement of PCs (pentagonal columns) in the TTB-type framework which is also known from Nb{sub 8}W{sub 9}O{sub 47}. For 1200{degrees}C, the electron diffracton patterns (along [001]) exhibit circular diffuse scattering around the basic reflections and additional superstructure reflections can be observed at the intersections of the circles with both tetragonal axes. A structural model for the low-temperature phase has been derived from HRTEM images. It is shown (using Fourier analysis) that the diffuse scattering is caused by a disordered distribution of the PCs. In case of a locally incomplete reaction, the arising defect structure of a tungsten-rich crystal area is characterized using HRTEM.

• OSTI ID: 390900
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 124; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRYSTAL DEFECTS
STRUCTURAL CHEMICAL ANALYSIS
TANTALUM OXIDES
TETRAGONAL LATTICES
TRANSMISSION ELECTRON MICROSCOPY
TUNGSTEN OXIDES
X-RAY DIFFRACTION