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Formation and Transformation of WO 3 Prepared from Alkoxide
Author(s) -
Yamaguchi Osamu,
Tomihisa Daijo,
Kawabata Hidenao,
Shimizu Klyoshi
Publication year - 1987
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1987.tb05010.x
Subject(s) - orthorhombic crystal system , alkoxide , amorphous solid , tungsten , hydrate , crystallization , crystallography , materials science , chemistry , hydrolysis , crystal structure , catalysis , organic chemistry , metallurgy
Amorphous WO 3 or WO 3 or H 2 O is formed by hydrolysis of tungsten ethoxide. The temperature of hydrolysis influences the crystallization of WO 3 ·H 2 O. Tungsten hydrate (WO 3 ·H 2 O) has an orthorhombic unit cell with a=0.5235 nm, b = 1.0688 nm, and c=0.5123 nm. Orthorhombic WO 3 crystallizes at 350° to 500°Cfrom amorphous WO 3 . Cubic WO 3 is formed at 200° to 310°C with dehydration of WO 3 ·H 2 O. WO 3 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.