Study On The Phase Change And Color Change Of Tungsten Oxide Nanoparticles Under High Pressure

Tungsten trioxide is a kind of semiconductor with hexagonal or cubic symmetrical structure at room temperature and atmospheric pressure.With its potential properties,today,tungsten trioxide has attracted great attention.Tungsten trioxide is an excellent material which has not only photochromic and electrochromic properties,but also simple preparation and cheap price.As a result it can be used in the manufacture of smart window and screen.So the chromic property of tungsten trioxide has great research value.Different from other research on photochromic and electrochromic properties of Tungsten trioxide,we studied the color of nanocrystalline tungsten trioxide with different pressure.We used the symmetric diamond anvil cell(DAC)to present the sample at the range of pressure from 0.5 GPa to 31.8 GPa.After we firstly got the phenomenon that the color of nanocrystalline tungsten trioxide can be changed with the process of increasing pressure,and the result of previous research that different pressure can create a great influence on the structure of normal size tungsten trioxide.We believe this phenomenon should be caused by the change of structure.On the other hand,the nano size will change some properties of tungsten trioxide,which may cause the different influence of pressure on the structure.So we characterized the influence of pressure on the structure of nanocrystalline tungsten trioxide with Raman spectra.After we compared them with the data got from the normal size.We found that the spectra changed with increasing pressure at 1.6 GPa,2.9 GPa,9.4 GPa and 23.5 GPa respectively,and structure change caused by pressure was irreversible.All of them can be also found in the research on the normal size tungsten trioxide.To characterize the color variation of tungsten trioxide caused by pressure,we tested the sample at different pressure with UV-Vis absorption spectra.Finally,we found the position of maximum absorption spectrum line as the position of absorption peak,and got the effect of increasing pressure on the absorption peak.We compared it with the Raman spectra we got former,and found the relationship between them.With the previous research on the electric property of nanocrystalline tungsten trioxide,we finally got the relationship among color,pressure and structure of the nanocrystalline tungsten trioxide.