Tungsten Oxide Nanocrystals Synthesized

Tungsten oxide, also known as tungsten trioxide or tungstic anhydride, WO3, is a chemical compound containing oxygen and the transition metal tungsten. It is obtained as an intermediate in the recovery of tungsten from its minerals.Tungsten ores are treated with alkalis to produce WO3. Further reaction with carbon or hydrogen gas reduces tungsten trioxide to the pure metal.

Tungsten oxide (hydrate) nanocrystals have been synthesized via hydrothermal route assisted by ammonium benzoate (AB), which showed the products with various morphologies, including the flower-shape, spherical and star-shape. Based on the analysis of the Fourier transform infrared spectra and observations of the time-dependent growth, a new self-assembly growth mechanism has been proposed for the formation of the different microstructures. The star-netted WO3 nanocrystals were applied as a sensitive layer for the relative humidity performed using a ZnO/LiTaO3.Love mode SAW device. The frequency shift has been observed with a sensitive response to the change of the relative humidity from 30% to 90%, and the frequency shift is linearly related to the relative humidity.

A new one-step method using the special holder has been developed to sputter-deposit the ZnO films. The typical columnar structure is inclined and the column inclination angle has been changed from 0^o to 34^o. X-ray diffraction analysis shows that the strains in the ZnO films decreased with substrate tilt angle. The optical characterization indicates tha the band-gap energies decreased from 3.19 eV to 3.07 eV, which has a linear relation to the strain in the ZnO films.

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