Comparing the atomic structures of binary MO2-SiO2 (M = Ti, Zr or Hf) xerogels

Mountjoy, G. and Holland, M.A. and Gunawidjaja, P.N. and Wallidge, G.W. and Pickup, D.M. and Newport, R.J. and Smith, M.E. (2003) Comparing the atomic structures of binary MO2-SiO2 (M = Ti, Zr or Hf) xerogels. Journal of Sol-Gel Science and Technology, 26 (1-3). pp. 161-164. ISSN 0928-0707. (Access to this publication is restricted)

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http://dx.doi.org/10.1023/A:1020774310142

Abstract

The incorporation of transition-metal oxides into silica can give materials with useful optical, electronic or catalytic properties. For example, ZrO2-SiO2 and HfO2-SiO2 materials are of interest due to their high dielectric constants. Here we present a comparison of extended X-ray absorption fine structure and small-angle X-ray scattering results for acid-catalysed binary (MO2)(x)(SiO2)(1-x) (M=Ti, Zr or Hf) xerogels, with x up to 0.4 and heat treatments up to 750degreesC. Detailed observations for TiO2-SiO2 and ZrO2-SiO2 xerogels provide a basis for interpretation of new results for HfO2-SiO2 xerogels. At low concentrations metal atoms are homogeneously incorporated into the silica network. Ti adopts coordinations of 4 or 6, and Zr and Hf both adopt higher coordination of 6 or 7 (the larger coordinations being due to ambient moisture). At higher concentrations, phase separation of metal oxide occurs. Such regions become clearly separated from the silica network for TiO2, but remain very finely mixed with silica network for ZrO2 and HfO2.

Item Type: Article
Uncontrolled keywords: hafnia-silica; xerogel; structure; EXAFS; SAXS ZIRCONIA-SILICA XEROGELS; SOL-GEL PROCESS; TITANIA-SILICA; ACIDIC PROPERTIES; X-RAY; XANES; EXAFS; SYSTEM
Subjects: Q Science
Q Science > QC Physics
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences > Functional Materials Group
Depositing User: Bob Newport
Date Deposited: 26 Jun 2008 18:56
Last Modified: 12 Jun 2012 15:22
Resource URI: http://kar.kent.ac.uk/id/eprint/8217 (The current URI for this page, for reference purposes)
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