Structural relations in the Nb--W--O and Ta--W--O systems for the phase region near WO/sub 3/

Journal Article · Tue Jun 01 04:00:00 EDT 1976 · J. Solid State Chem.; (United States)

DOI:https://doi.org/10.1016/0022-4596(76)90086-4· OSTI ID:7347936

Ekstrom, T; Tilley, R J.D.

Phase relationships in the two systems Nb--W--O and Ta--W--O have been determined for metal to oxygen ratios between MO/sub 3/./sub 0/ and MO/sub 2/./sub 72/ at a temperature of 1373/sup 0/K, using a combination of x-ray diffraction, electron microscopy, and optical microscopy. The two systems are found to be very similar. An extensive series of crystallographic shear (CS) phases existing over a wide phase field did not form and all CS structures found had compositions close to the binary W--O line. These CS phases were based upon (102) and (103) CS planes and no evidence for CS upon any other planes was found. Within the phase region examined the majority of the niobium or tantalum combines to form ternary tungsten oxides of the tetragonal tungsten bronze type which are often disordered and which coexist either with the CS phases or with W/sub 18/O/sub 49/. In addition, the high-temperature forms of WO/sub 3/ were often found to be stabilized to room temperature in slightly reduced samples. The results are summarized in phase diagrams.

• Research Organization: Univ., Stockholm
• OSTI ID: 7347936
• Journal Information: J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 18:2; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
BINARY MIXTURES
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL STRUCTURE
DIAGRAMS
DIFFRACTION
DISPERSIONS
ELECTRON MICROSCOPY
MICROSCOPY
MIXTURES
NIOBIUM COMPOUNDS
NIOBIUM OXIDES
OXIDES
OXYGEN COMPOUNDS
PHASE DIAGRAMS
SCATTERING
TANTALUM COMPOUNDS
TANTALUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN COMPOUNDS
TUNGSTEN OXIDES
VERY HIGH TEMPERATURE
X-RAY DIFFRACTION