Formation and Transformation of WO3 Prepared from Alkoxide |
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| Authors: | Osamu Yamaguchi Daijo Tomihisa Hidenao Kawabata Klyoshi Shimizu |
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| Affiliation: | Department of Applied Chemistry, Faculty of Engineering, Doshisha University, Kyoto 602, Japan |
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| Abstract: | Amorphous WO3 or WO3 or H2O is formed by hydrolysis of tungsten ethoxide. The temperature of hydrolysis influences the crystallization of WO3·H2O. Tungsten hydrate (WO3·H2O) has an orthorhombic unit cell with a=0.5235 nm, b = 1.0688 nm, and c=0.5123 nm. Orthorhombic WO3 crystallizes at 350° to 500°Cfrom amorphous WO3. Cubic WO3 is formed at 200° to 310°C with dehydration of WO3·H2O. WO3 transformations are examined by high-temperature X-ray diffraction. The kinetics of formation of the cubic modification have been studied by measuring the weight decrease with a thermobalcnce. Formation isotherms can be interpreted in terms of the first-order equation –In (1–f)=kt; activation energies are 110 and 80 kJ mol?1 for initial and final stages, respectively. |
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