Structural characterizations of sol-gel synthesized TiO2 and Ce/TiO2 nanostructures

Mixed phase TiO2 and Ce/TiO2 samples were synthesized by a sol-gel method using different hydrolysis conditions. In pure TiO2 samples, traditional X-ray diffraction (XRD) and Ti K-edge synchrotron X-ray absorption near edge structures (XANES) independently revealed their anatase/rutile phase ratios. XANES results further revealed a substantial amount of Ti atoms existed in other forms beside anatase and rutile TiO2 in the sample synthesized by the low hydrolysis condition. An increase in the extent of the hydrolysis during the synthesis leads to an increased rutile ratio and a reduction in other forms. In Ce/TiO2 samples, the crystal sizes were too small for XRD characterization. Only XANES could be used to characterize their phase ratios. It is found that adding Ce impedes rutile formation; leading to increased anatase ratio. The difference in the fundamental aspects of XRD and XANES techniques in providing the phase ratios is discussed.