Une nouvelle forme de trioxyde de tungstene: Les oxydes WO3 et WO3·O,5H2O a structure pyrochlore

Orthorhombic WO3Formed via a Ti-Stabilized WO3·13H2O Phase

“…They are built from corner-sharing [ (6). Tungsten oxides with a pyrochlore-type structure have also been obtained via the thermal decomposition of ammonium tungstate (7,8). Upon further heating around 400°C, all these metastable oxides lead to the stable monoclinic WO phase.…”

An Unexpected Crystal‐Chemical Principle for the Pyrochlore Structure

“…The extensive compositional ranges known for pyrochlore compounds reflect the versatility of the A 2 OЈ substructure: "defect" pyrochlores form readily since this network can be partially occupied or even completely absent, as in the pyrochlore-type polymorph of WO 3 (W 2 O 6 ). [29] In addition, the OЈ position can be occupied by anions other than O 2-such as OH -, F -, [30] and S 2-, [31] forming oxyhydroxide, oxyfluoride, and oxysulfide pyrochlores. A number of non-oxide pyrochlores are known [27,32] including chlorides [33] and fluorides.…”

Synthesis and characterization of tungsten trioxide powders prepared from tungstic acids

“…The synthesis of compounds with n ¼ 1/3, 1/2, 1 or 2 has been reported [10][11][12]. The structure of tungstic acids [10][11][12] is composed of basic units of WO 6 octahedra linked by shared corners, like in tungsten trioxide [12][13][14] Materials Research Bulletin 39 (2004) [683][684][685][686][687][688][689][690][691][692][693] but in a more open framework.…”

“…The synthesis of compounds with n ¼ 1/3, 1/2, 1 or 2 has been reported [10][11][12]. The structure of tungstic acids [10][11][12] is composed of basic units of WO 6 octahedra linked by shared corners, like in tungsten trioxide [12][13][14] Materials Research Bulletin 39 (2004) [683][684][685][686][687][688][689][690][691][692][693] but in a more open framework. Solution methods involving tungstic acids as precursors have been reported, for example, the preparation of mesoporous WO 3 films using as precursor a colloidal solution of tungstic acid [15] and the synthesis of WO 3 by treatment of tungstic acid (WO 3 ÁH 2 O) with organic ligands or water-in-oil emulsions [16].…”