Changes in the Zr environment in zirconia-silica xerogels with composition and heat treatment as revealed by Zr K-edge XANES and EXAFS

Mountjoy, Gavin and Pickup, David M. and Anderson, Ruth and Wallidge, Graham and Holland, Mark A. and Newport, Robert J. and Smith, Mark E. (2000) Changes in the Zr environment in zirconia-silica xerogels with composition and heat treatment as revealed by Zr K-edge XANES and EXAFS. Physical Chemistry Chemical Physics, 2 (10). pp. 2455-2460. ISSN 1463-9076. (Full text available)

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http://dx.doi.org/10.1039/a910300g

Abstract

X-ray absorption spectroscopy at the Zr K-edge is an important technique for probing the environment of Zr. Here it is applied to zirconia-silica xerogels with composition 0.07 less than or equal to x less than or equal to 0.40, where x is the molar ratio Zr : (Zr + Si). Reference samples of crystalline ZrO2, ZrSiO4, BaZrO3 and liquid Zr n-propoxide were also examined. New XANES (X-ray adsorption near edge structure) results are presented for zirconia-silica xerogels, and compared with previous EXAFS (extended X-ray absorption fine structure) results. For high Zr contents (x = 0.4) there is a separate, amorphous ZrO2 phase, which before heat treatment is similar to Zr hydroxide, and after heat treatment at 750 degrees C is similar to an amorphous precursor of tetragonal ZrO2. For low Zr contents (x = 0.1) there is atomic mixing of Zr in the SiO2 network, and the environment of Zr is more similar to that in Zr n-propoxide compared to other reference samples. New in situ XANES and EXAFS results are presented for x = 0.1 xerogels heated at 250 degrees C. These clearly show that the Zr environment depends on ambient moisture in addition to heat treatment.

Item Type: Article
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences > Functional Materials Group
Depositing User: J.M. Smith
Date Deposited: 08 May 2009 15:43
Last Modified: 11 Apr 2014 13:03
Resource URI: http://kar.kent.ac.uk/id/eprint/15927 (The current URI for this page, for reference purposes)
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