LAUSR

A hexagonal form of tungsten trioxide (h-WO3, particle size: 15.9-57.1 nm) was found to be formed by a direct reaction between metallic tungsten powder (W, particle size: 0.45-0.59 μm) and 15-30% hydrogen peroxide (H2O2) aq solution. Oxide film on the powder surface having the similar crystal structure as h-WO3 was essential for the formation, and the surface oxide film was formed by aging the powder in air at 45°C, a relative humidity of 100% (PH2O 96 hPa) for 3-28 days or in ambient atmosphere at room temperature for 12 years. The Rietveld analysis performed in the space group P63/mcm (Z=6) indicated the crystal structures were the same as those of the reported h-WO3 and that the crystallographic characteristic were: a=0.74219 nm, c=0.77198 nm for h-WO3 from the 28-day aged powder and a=0.74538 nm, c=0.77194 nm for h-WO3 from the 12-year aged powder. This article is protected by copyright. All rights reserved.