%0 Thesis
%9 Doctoral
%A Burgess, Ayrton
%B Chemistry
%D 2025
%E Sankar, Gopinathan
%F discovery:10205179
%I UCL (University College London)
%K Materials Science, Chemistry, Diffraction Anomalous Fine Structure, X-ray Absorption, X-ray diffraction
%P 252
%T Development and Applications of Diffraction Anomalous Fine Structure: Extracting Site-Specific X-ray Absorption Spectra of Functional Oxides
%U https://discovery.ucl.ac.uk/id/eprint/10205179/
%X 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
%Z 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.