TY  - UNPB
PB  - UCL (University College London)
UR  - https://discovery.ucl.ac.uk/id/eprint/10205179/
N2  - This thesis presents the development and applications of the Diffraction Anomalous Fine Structure (DAFS) technique for determining the site-specific structural
properties of a given metal ion. A graphical user interface has been developed to
extract anomalous scattering factors f? and f? from powder samples, based on an
iterative Kramers-Kronig algorithm described in the literature [ ¨ 1], [2], to improve
DAFS ?user-friendliness?. XAS extracted from DAFS are further processed using
typical XAS analysis software [3].
In the first instance, the optimal XRD data collection procedure was investigated using different detector systems, across a given absorption edge and data
collected using the Pilatus detector was found to be superior. Fe3O4, which has both
tetrahedral and octahedral environments located in different crystallographic sites,
was used to test the validity of the DAFS measurement. The investigation showed
that the conventional XAS data could be represented by a linear combination of
the individual site contributions extracted from DAFS. Further studies on ZnFe2O4
revealed the presence of Zn2+ ions in both crystallographic sites, with the tetrahedral
site dominating the sample. Zn2+ ions doped in ZrO2, a prominent CO2 hydrogenation catalyst, was investigated by collecting diffraction data across the Zn K-edge
to understand the nature of Zn incorporation. Reflections in the XRD pattern of
tetragonal ZrO2 were used to extract the DAFS, and it clearly shows that Zn2+ ions
are substituted into Zr4+ sites. Further XANES simulations using oxygen-deficient
structures support the presence of oxygen vacancies. Finally, directional anisotropy
in the growth of nanocrystalline ZnO prepared from the decomposition of Zinc
peroxide was investigated using two prominent reflections in the XRD data, and extracted DAFS was again analysed via conventional XAS analysis procedures.
This project has established a method to simplify the DAFS measurement at a
conventional XAS beamline. Furthermore, the computational analysis procedures
generated as part of this work are also presented with the hope that DAFS will
become a more widely utilised structural technique in synchrotron light sources
worldwide
ID  - discovery10205179
A1  - Burgess, Ayrton
KW  - Materials Science
KW  -  Chemistry
KW  -  Diffraction Anomalous Fine Structure
KW  -  X-ray Absorption
KW  -  X-ray diffraction
M1  - Doctoral
Y1  - 2025/02/28/
AV  - public
EP  - 252
TI  - Development and Applications of Diffraction Anomalous Fine Structure: Extracting Site-Specific X-ray Absorption Spectra of Functional Oxides
N1  - Copyright © The Author 2025.   Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/).  Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms.  Access may initially be restricted at the author?s request.
ER  -