The phase transitions between H{sub 0.13}V{sub 0.13}Mo{sub 0.87}O{sub 3}{center_dot}0.26H{sub 2}O and MoO{sub 3}: An X-ray, thermal analysis, and TEM study
- Univ. de Picardie Jules Verne, Amiens (France). Lab. de Reactivite et Chimie des Solides
Mixed vanadium-molybdenum oxide hydrates (H{sub x}V{sub x}Mo{sub 1{minus}x}O{sub 3}{center_dot}0.26H{sub 2}O with 0.06 {le} x {le} 0.18) have been synthesized by a soft chemistry method. The phase transitions from one of these hydrates (x = 0.13) to the final product MoO{sub 3} have been studied by thermal analysis, X-ray powder diffraction, and transmission electron microscopy techniques. Both metastable and stable oxides have been observed. H{sub 0.13}V{sub 0.13}Mo{sub 0.87}O{sub 3}{center_dot}0.26H{sub 2}O possesses a structure related to hexagonal MoO{sub 3}. Dehydration of the precursor leads to a metastable phase H{sub 0.13}V{sub 0.13}Mo{sub 0.87}O{sub 3}, with a structure similar to that of the hydrate. At 500 C this phase transforms into the metastable V{sub 0.13}Mo{sub 0.87}O{sub 2.935}, with a structure related to the orthorhombic MoO{sub 3} structure. The heating of this last phase above 500 C induces a change from the metastable system to the stable binary (V{sub 2}O{sub 5}-MoO{sub 3}) one. In agreement with this binary, a liquid phase and a solid phase with a composition closest to MoO{sub 3}, are formed during the phase segregation at 600 C. Models for explaining these phase transitions are proposed.
- OSTI ID:
- 349912
- Journal Information:
- Journal of Solid State Chemistry, Vol. 143, Issue 1; Other Information: PBD: 15 Feb 1999
- Country of Publication:
- United States
- Language:
- English
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