Structural characterizations of sol–gel synthesized TiO2 and Ce/TiO2 nanostructures
摘要:
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. (C) 2011 Elsevier B.V. All rights reserved.
Structure Evolution in Hydrothermally Processed (<100oC) BaTiO3 Films
作者:Elliott B. Slamovich、Ilhan A. Aksay
DOI:10.1111/j.1151-2916.1996.tb07904.x
日期:1996.1
Thin films of cubic BaTiO3 were processed hydrothermally at 40°–80°C by reacting thin layers of titanium organo metallic liquid precursors in aqueous solutions of either Ba(OH)2 or a mixture of NaOH and BaCl2. All films (thickness ∼1 μm) were polycrystalline with grain sizes ranging from nano‐ to micrometer dimensions. BaTiO3 formation was facilitated by increasing [OH‐], [Ba2+], and the temperature. The film structure was related to the nucleation and growth behavior of the BaTiO3 particles. Films processed at relatively low [OH‐], [Ba2+], and temperatures were coarse grain and opaque, but increasing [OH‐], [Ba2+], and temperature caused the grain size to decrease, resulting in transparent films.