Distinctions In The Raman Spectroscopy Features Of Wo3 Materials With Increasing Temperature

Garcia-Sanchez, Raul F

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https://hdl.handle.net/2142/50861 Copy

Description

Title

Distinctions In The Raman Spectroscopy Features Of Wo3 Materials With Increasing Temperature

Author(s)

Garcia-Sanchez, Raul F

Contributor(s)

Misra, Prabhakar

Issue Date

2014-06-16

Keyword(s)

Analytical, Combustion, Plasma

Abstract

\begin{wrapfigure}{l}{0pt} \includegraphics[scale=0.9]{TOCFigure.eps} \end{wrapfigure} Metal oxides are widely used in gas sensor applications due to their low cost, easy production and selectivity. Tungsten Oxide (WO$_{3}$) is one of the most used metal oxides in the detection of Nitrogen gases (NO$_{x}$). The purpose of this research is to determine if the Raman features of a metal oxide gas sensor can serve as tools to make estimates regarding the sensor capabilities related to the target gases. This research will be used for gas sensing of oxidizing/reducing toxic gases (i.e. H$_{2}$S, NO$_{x}$, SO$_{2}$, etc.) and finding the effect that temperature, gas concentration, type of gas, exposure time and other variables have on the Raman spectra of metal oxides. In this experiment, the temperature was increased from $30-160\,^{\circ}\mathrm{C}$ and the Raman data was taken using a 780 nm infrared laser. In two of the samples, WO$_{3}$ on Silicon substrate and WO$_{3}$ nanopowder, we found vibrational modes at ~807, ~716 and ~271 cm$^{-1}$, which are indicators of a monoclinic WO$_{3}$ structure. The WO$_{3}$ nanowires samples exhibit the O-W-O bond stretching feature is present and asymmetric stretching of the W-O bonds occurs, resulting in a 750 cm$^{-1}$ band. The intensity of Raman features such as 750 cm$^{-1}$ for nanowires and 492 and 670 cm$^{-1}$ for WO$_{3}$ on Silicon substrate begins to decay as temperature increases. Additionally, the vibrational modes related to O-H and W-OH become more pronounced as temperature increases due to those bonds reacting more strongly to the temperature change than the normal W-O bonds related to the original lattice structure. Finally, all samples have low-frequency phonon mode markers associated with temperature change, and in most cases these change as temperature increases. The understanding of the thermal effects will help develop theoretical models for the identification of specific metal oxide-gas relationships and provide a supplemental way of observing gas adsorption in addition to current conductivity measurements.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/50861

DOI

https://doi.org/10.15278/isms.2014.MJ07

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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