A rare-earth K-edge EXAFS study of rare-earth phosphate glasses, (R2O3)(x)(P2O5)(1-x), x=0.187-0.239, R = La, Nd, Sm, Eu, Gd, Dy, Er

Cole, Jacqueline M. and Bowron, Daniel Timothy and Newport, Robert J. and Pettifer, Robert F. and Mountjoy, Gavin and Brennan, Tessa and Saunders, George A. (2001) A rare-earth K-edge EXAFS study of rare-earth phosphate glasses, (R2O3)(x)(P2O5)(1-x), x=0.187-0.239, R = La, Nd, Sm, Eu, Gd, Dy, Er. Journal of Physics: Condensed Matter, 13 (31). pp. 6659-6674. ISSN 0953-8984. (Full text available)

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Abstract

A rare-earth K-edge extended X-ray absorption fine structure (EXAFS) study of rare-earth phosphate glasses, (R2O3)(x)(P2O5)(1-x), x = 0.187-0.239, R = La, Nd, Sm, Eu, Gd, Dy, Er, is presented. The structures of these materials were investigated as a function of (a) rare-earth atomic number and (b) temperature, and represent some of the first rare-earth K-edge EXAFS studies on a series of lanthanide-based materials. Results corroborate findings from complementary X-ray and neutron diffraction and magic-angle-spinning (NIAS) NMR experiments, and in addition, they provide a unique insight into the nature of the static disorder of the R-O correlations and of the neighbouring phosphate groups. The effects of multiple-scattering contributions are also discussed within this context. The variable temperature measurements illustrate the exceptionally high level of network rigidity present in these materials. The results are also compared to those obtained from an analogous rare-earth L-III-edge EXAFS (5.483-8.358 keV) study. Results show that the use of the much higher energies of the rare-earth K-edge (38.925-57.486 keV) enable one to avoid the double-electron excitation problems that are associated with the rare-earth L-III-edge EXAFS in the dynamic range of interest. EXAFS fitting and deconvolution simulations show that the large core hole lifetimes associated with the rare-earth K-edge do not significantly detract from the results. The deconvolution. studies also corroborate our findings that the level of fitting to our data cannot realistically be expanded beyond the first R-O shell. This limitation exists despite the exceptional counting statistics of the experiment and the highly uniform samples made possible by the ability to use much thicker samples at the higher energies compared to those used for the (higher absorption) rare-earth L-III-edge EXAFS studies.

Item Type: Article
Uncontrolled keywords: ABSORPTION-FINE-STRUCTURE; EXTENDED-X-RAY; BODY DISTRIBUTION-FUNCTIONS; EFFECTIVE IONIC-RADII; CURVED-WAVE THEORY; FLUOROZIRCONATE GLASSES; METAPHOSPHATE GLASSES; CONDENSED MATTER; LOCAL-STRUCTURE; SPECTROSCOPY
Subjects: Q Science > Q Science (General)
Q Science > QC Physics
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences > Functional Materials Group
Faculties > Science Technology and Medical Studies > School of Physical Sciences
Depositing User: Bob Newport
Date Deposited: 26 Jun 2008 16:06
Last Modified: 02 Jun 2014 13:16
Resource URI: http://kar.kent.ac.uk/id/eprint/8210 (The current URI for this page, for reference purposes)
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