Crystal structure and topotactic dehydration of magnesium tungstate dihydrate, MgWO/sub 4/ x 2H/sub 2/O

Journal Article · Sat Nov 01 04:00:00 EST 1986 · J. Solid State Chem.; (United States)

DOI:https://doi.org/10.1016/0022-4596(86)90096-4· OSTI ID:6972248

Guenter, J R; Dubler, E

MgWO/sub 4/ x 2H/sub 2/O crystallizes in the monoclinic space group P2/sub 1//c, a = 5.917(1), b = 10.243(2), c = 8.566(1) A, ..beta.. = 90.05(2)/sup 0/. Its crystal structure consists of individual layers built up from edge-sharing pairs of MgO/sub 4/(H/sub 2/O)/sub 2/ octahedra corner linked with WO/sub 4/ tetrahedra. Thermal dehydration leads in a first topotactic step to monoclinic (eventually triclinic) MgWO/sub 4/ x H/sub 2/O, for which a structural model has been deduced, based on its unit cells (a = 9.246, b = 10.773, c = 8.564 A, ..cap alpha.. = 92.43/sup 0/) and the relative orientation relations between the two lattices. It corresponds to a so far unobserved atomic arrangement, predicted to exist by earlier authors on theoretical grounds. The loss of the remaining water is again topotactic, but leads to a multiply twinned product, which corresponds in its powder diffraction pattern closely to high-temperature MgWO/sub 4/, reported to exist above 12200/sup 0/C only, and is transformed into the stable wolframite structure at 650/sup 0/C. These observations are attributed to the topotactic nature of the dehydration process.

• Research Organization: Univ. of Zuerich, Switzerland
• OSTI ID: 6972248
• Journal Information: J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 65:1; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DATA
DEHYDRATION
DIFFRACTION
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
HYDRATES
INFORMATION
LATTICE PARAMETERS
MAGNESIUM COMPOUNDS
MICROSCOPY
MONOCLINIC LATTICES
NUMERICAL DATA
POWDERS
SCANNING ELECTRON MICROSCOPY
SCATTERING
X-RAY DIFFRACTION