Synthesis and characterization of tungsten trioxide powders prepared from tungstic acids

Abstract

WO 3 powders were prepared by the thermal decomposition of tungstic acids (WO 3 ÁnH 2 O, n ¼ 1/3, 1, 2). The tungstic acids were synthesized from WO 4 2À aqueous solutions under a variety of conditions of pH, temperature and W(VI) concentrations. The thermal decomposition of the tungstic acids into WO 3 was analysed by TG and DSC methods. Nano-sized WO 3 powders with different morphological characteristics were obtained by thermal treatment of the tungstic acids at 500 8C in air atmosphere. The morphologies of WO 3 powders were characterised by scanning electron microscopy and infrared absorption spectroscopy. Patterns of infrared spectra were related with distinct powder morphologies. #

Dip-coated hydrotungstite thin films as humidity sensors

“…Most of these hydrated compounds are prepared through solution routes, and a large amount of literature is available on the preparation and characterization of these compounds (Gerand et al 1981). Recently, a detailed study of tungsten oxide powders prepared from different tungstic acids has been reported (Nogueira et al 2004).…”

Hydrothermal synthesis and luminescence of CaMO4:RE3+ (M=W, Mo; RE=Eu, Tb) submicro-phosphors

“…The CaWO 4 :Eu 3+ phosphor has approximate vibration modes as the CaMoO 4 :Eu 3+ phosphor. Report on the FT-IR property of tungstate acids by Jesus et al[27] shows that both have five vibrations modes, as described inTable 1. The bands at 3454 cm À1 and 1630.7 cm -1 are assigned to O-H stretching vibration and H-O-H bending vibration[4], respectively.…”

Development of composite anode electrocatalyst for direct methanol fuel cells

“…2b) decreases significantly along with the appearance of the diffraction pattern of WO 3 (JCPDS-ICDD File No. 43-1035), suggesting that the dehydration of WO 3 Á H 2 O occurred at 400°C and formed WO 3 phase [28]. The diffraction peaks (020)/(200) and (202)/(220) of WO 3 were maintained in the sample of Pt-WO 3 /MWCNT ao after Pt deposition, as displayed in Fig.…”