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

Journal Article · Mon Feb 15 04:00:00 EST 1999 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1998.8067· OSTI ID:349912

Dupont, L; Larcher, D; Touboul, M ^[1]

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1. 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, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 143; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DEHYDRATION
EXPERIMENTAL DATA
HYDRATES
MOLYBDENUM OXIDES
PHASE STUDIES
THERMAL ANALYSIS
TRANSMISSION ELECTRON MICROSCOPY
VANADIUM OXIDES
X-RAY DIFFRACTION