Brown, AP orcid.org/0000-0001-9692-2154, Hillier, S and Brydson, RMD (2017) Quantification of Fe-oxidation state in mixed valence minerals: a geochemical application of EELS revisited. In: Journal of Physics: Conference Series. Electron Microscopy and Analysis Group Conference 2017 (EMAG2017), 03-06 Jul 2017, Manchester, UK. IOP Publishing
Abstract
The use of TEM and electron energy loss spectroscopy to determine levels of Fe3+ in solids at nanometre spatial resolution is well established. Here we assess this technique at the energy resolution of a monochromated electron source (0.3 eV) and with the capability of simultaneously acquiring core- and low-loss spectra for absolute energy calibration of core-loss chemical shifts. Fe L 2,3-edges of four oxide standards give a characteristic energy loss near edge structure (ELNES) and the L 3-peak maxima of the spectra exhibit an energy shift of ~ 1.8 eV between ferrous (709 eV) and ferric (710.8 eV) iron. We show that diagenetic chlorites present in iron oxide loaded 'red beds' contain predominately Fe3+, based on the absolute energy position of the low signal Fe L 3-edges (centred around 710.8 eV). We also fit our standard-spectra to Fe L 2,3-edges from magnetite and maghemite nanoparticles to investigate iron site occupancy. An additional chemical shift needs to be applied to the octahedral ferrous iron site component to achieve a plausible, linear fit to the magnetite spectrum which we speculate may be due to electron hopping between the mixed valence octahedral iron sites in magnetite.
Metadata
Item Type: | Proceedings Paper |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | Published under licence by IOP Publishing Ltd. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) |
Funding Information: | Funder Grant number EPSRC EP/M028143/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 31 Jan 2018 14:05 |
Last Modified: | 12 Feb 2019 12:49 |
Status: | Published |
Publisher: | IOP Publishing |
Identification Number: | 10.1088/1742-6596/902/1/012016 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:126848 |