XANES study of Ti coordination in heat-treated (TiO2)(x)(SiO2)(1-x) xerogels

Mountjoy, Gavin and Pickup, David M. and Wallidge, Graham and Anderson, Ruth and Cole, Jacqueline M. and Newport, Robert J. and Smith, Mark E. (1999) XANES study of Ti coordination in heat-treated (TiO2)(x)(SiO2)(1-x) xerogels. Chemistry of Materials, 11 (5). pp. 1253-1258. ISSN 0897-4756. (doi:https://doi.org/10.1021/cm980644u) (Access to this publication is currently restricted. You may be able to access a copy if URLs are provided)

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Accurate measurements of the height and position of the preedge peak in Ti K-edge XANES (X-ray absorption near-edge structure) can distinguish 4-, 5-, and 6-fold coordination of Ti by O (Ti-[4], Ti-[5], and Ti-[6], respectively), and mixtures thereof. This approach has been applied to titania-silica xerogels, (TiO2)(x)(SiO2)(1-x), prepared from Si and Ti alkoxides using a prehydrolysis step and acid catalyst, with 0.18 < x < 0.75. As expected, samples with x = 0.75 contain phase-segregated, amorphous, pre-anatase Ti-[6], which is converted to anatase after heating at 500 degrees C. Samples with x = 0.18 contain a majority of isolated, distorted Ti-[6] before heating, which is converted to Ti-[4] substituted for Si after heating at 750 degrees C. This is the first time that the changes in the coordination of isolated Ti have been unambiguously described. Xerogels with 0.25 < x < 0.35 and heat treatment at 750 degrees C showed concentration limits of Ti-[4] substitution for Si of 10-15mol %. Slightly higher values were obtained for xerogels prepared using acetylacetone, but the main difference was that the latter had a significantly larger content of distorted Ti-[6] before heat treatment. There is no evidence of significant amounts of Ti-[5].

Item Type: Article
Subjects: Q Science > Q Science (General)
Divisions: Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: I.T. Ekpo
Date Deposited: 05 Apr 2009 20:05 UTC
Last Modified: 13 Jan 2017 22:20 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/16947 (The current URI for this page, for reference purposes)
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