In situ EXAFS and XANES measurements of the change in Ti coordination during the calcination of a (TiO<sub>2</sub>)<sub>0.18</sub>(SiO<sub>2</sub>)<sub>0.82</sub> aerogel
D M Pickup; G Mountjoy; M A Holland; G W Wallidge; R J Newport; M E Smith
Журнал:
Journal of Physics: Condensed Matter
Дата:
2000-11-27
Аннотация:
The calcination of a (TiO<sub>2</sub>)<sub>0.18</sub>(SiO<sub>2</sub>)<sub>0.82</sub> aerogel has been followed using in situ high-temperature Ti K-edge `quick EXAFS' and XANES measurements. The results clearly show that the coordination of Ti in this material changes from a mixture of four- and sixfold to predominantly fourfold as the temperature is increased from ambient to 300 °C. The decrease in static disorder, as the environment of Ti converts to predominantly a single site, is such that the overall Debye-Waller factor for the Ti-O shell decreases markedly even as the temperature increases to 700 °C. Combined `quick EXAFS' and XANES measurements are shown to be valuable tools for in situ studies of structural changes associated with thermal treatment of amorphous materials.
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