Structure of WO3 ultrafine particles and their characteristic solid states

WO3 nanoparticles from 10 to 250nm in diameter were formed by burning tungsten wire in low-oxygen-partial-pressure atmosphere in Ar gas. The structure of the 10-nm-order particle was cubic WO3, and for the particle larger than 50 nm, the structure was triclinic WO3. The color of the produced samples changed from blue to yellowish green and yellow depending on the particle size. It was also shown that the present particle is a good transmittance material for mid-IR light with wavelength between 5 and 20 mu m. The growth of huge particles by coalescence growth in smoke has been discussed. (C) 2004 Elsevier B.V. All rights reserved.