In situEXAFS and XANES measurements of the change in Ti coordination during the calcination of a (TiO2)0.18(SiO2)0.82aerogel

The calcination of a (TiO 2 ) 0.18 (SiO 2 ) 0.82 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.