<div class="csl-bib-body">
<div class="csl-entry">Eder, F., Weil, M., Schubert, W.-D., & Gierl-Mayer, C. (2021). Ammonium metatungstate, (NH4)6[H2W12O40] - crystallization and thermal behavior of various hydrous species. <i>Crystal Growth and Design</i>, <i>21</i>(11), 6195–6212. https://doi.org/10.1021/acs.cgd.1c00639</div>
</div>
-
dc.identifier.issn
1528-7483
-
dc.identifier.uri
http://hdl.handle.net/20.500.12708/138053
-
dc.description.abstract
Various hydrous ammonium metatungstate phases (NH4)6[H2W12O40]·XH2O (AMT-X) have been obtained in the form of single crystals, using supersaturated solutions, antisolvent crystallization, and partial dehydration as strategies for crystal growth. On the basis of laboratory X-ray diffraction data, the crystal structures of the hydrous phases with X = 22, 12.5, 9.5, 8.5, 6, 4, and 2 as well of the cocrystals with X = 12-ethanol and X = 4-2acetone have been determined for the first time. AMT-22 forms the solid solution series (NH4)6-xKx[H2W12O40]·22H2O with the potassium salt (PMT-22) without a miscibility gap. Its tetragonal crystal structure shows a distorted cubic close-packed arrangement of the spherical α-Keggin-type [H2W12O40]6- anions with disordered ammonium N and water O atoms in the voids. The crystal structures of the other, less-hydrated AMT phases can be derived from distorted hexagonal rod packings of the α-Keggin anions, likewise with the cations and crystal water molecules in the voids. The thermal behavior of AMT-22 crystals reveals a quick dehydration, with AMT-9.5 as an intermediate and AMT-4 as a stable hydrate phase under ambient conditions. Upon further heating, the material decomposes with stepwise formation of AMT-2, AMT-1, AMT-0, and an amorphous phase, before orthorhombic WO3 forms above 400 °C. One of the commercially available AMT phases, "(NH4)6[H2W12O40]·XH2O" (with X = unspecified) has a water content of X = 4 but crystallizes in a structure other than AMT-4. Consequently, the 4-hydrate shows polymorphic behavior.
en
dc.language.iso
en
-
dc.publisher
AMER CHEMICAL SOC
-
dc.relation.ispartof
Crystal Growth and Design
-
dc.subject
Condensed Matter Physics
-
dc.subject
General Materials Science
-
dc.subject
General Chemistry
-
dc.title
Ammonium metatungstate, (NH4)6[H2W12O40] - crystallization and thermal behavior of various hydrous species