Non-classical behaviour of higher valence dopants in chromium (III) oxide by a Cr vacancy compensation mechanism

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dc.contributor.author Carey, John J.
dc.contributor.author Nolan, Michael
dc.date.accessioned 2017-09-11T09:04:18Z
dc.date.available 2017-09-11T09:04:18Z
dc.date.issued 2017-09-05
dc.identifier.citation Carey, J. J. and Nolan, M. (2017) 'Non-classical behaviour of higher valence dopants in chromium (III) oxide by a Cr vacancy compensation mechanism', Journal of Physics: Condensed Matter, 29(41), 415501 (14pp). doi:10.1088/1361-648X/aa8250 en
dc.identifier.volume 29 en
dc.identifier.issued 41 en
dc.identifier.issn 0953-8984
dc.identifier.uri http://hdl.handle.net/10468/4675
dc.identifier.doi 10.1088/1361-648X/aa8250
dc.description.abstract Modification of metal oxides with dopants that have a stable oxidation in their parent oxides which is higher than the host system is expected to introduce extra electrons into the material to improve carrier mobility. This is essential for applications in catalysis, SOFCs and solar energy materials. Density functional theory calculations are used to investigate the change in electronic and geometric structure of chromium (III) oxide by higher valence dopants, namely; Ce, Ti, V and Zr. For single metal doping, we find that the dopants with variable oxidation states, Ce, Ti and V, adopt a valence state of  +3, while Zr dopant has a  +4 oxidation state and reduces a neighbouring Cr cation. Chromium vacancy formation is greatly enhanced for all dopants, and favoured over oxygen vacancy formation. The Cr vacancies generate holes which oxidise Ce, Ti and V from  +3 to  +4, while also oxidising lattice oxygen sites. For Zr doping, the generated holes oxidise the reduced Cr2+ cation back to Cr3+ and also two lattice oxygen atoms. Three metal atoms in the bulk lattice facilitate spontaneous Cr vacancy from charge compensation. A non-classical compensation mechanism is observed for Ce, Ti and V; all three metals are oxidised from  +3 to  +4, which explains experimental observations that these metals have a  +4 oxidation state in Cr2O3. Charge compensation of the three Zr metals proceeds by a classical higher valence doping mechanism; the three dopants reduce three Cr cations, which are subsequently charge compensated by a Cr vacancy oxidising three Cr2+ to Cr3+. The compensated structures are the correct ground state electronic structure for these doped systems, and used as a platform to investigate cation/anion vacancy formation. Unlike the single metal doped bulks, preference is now given for oxygen vacancy formation over Cr vacancy formation, indicating that the dopants increase the reducibility of Cr2O3 with Ce doping showing the strongest enhancement. The importance of the correct ground state in determining the formation of defects is emphasised. en
dc.description.sponsorship European Cooperation in Science and Technology (COST ACTION CM1104) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher IOP Publishing en
dc.rights © 2017 IOP Publishing Ltd. This is an author-created, un-copyedited version of an article accepted for publication/published in Journal of Physics: Condensed Matter. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/1361-648X/aa8250 en
dc.subject Density functional theory en
dc.subject Charge compensation en
dc.subject Non classical mechanism en
dc.subject Chromium oxide en
dc.subject Metal doping en
dc.subject Vacancy formation en
dc.title Non-classical behaviour of higher valence dopants in chromium (III) oxide by a Cr vacancy compensation mechanism en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Michael Nolan, Tyndall Theory Modelling & Design Centre, University College Cork, Cork, Ireland. +353-21-490-3000 Email: michael.nolan@tyndall.ie en
dc.internal.availability Full text available en
dc.check.info Access to this article is restricted until 12 months after publication by request of the publisher. en
dc.check.date 2018-09-05
dc.date.updated 2017-09-11T08:45:30Z
dc.description.version Accepted Version en
dc.internal.rssid 410647268
dc.contributor.funder Seventh Framework Programme en
dc.contributor.funder Science Foundation Ireland en
dc.contributor.funder Higher Education Authority en
dc.contributor.funder European Cooperation in Science and Technology en
dc.description.status Peer reviewed en
dc.identifier.journaltitle Journal of Physics: Condensed Matter en
dc.internal.copyrightchecked Yes en
dc.internal.licenseacceptance Yes en
dc.internal.IRISemailaddress michael.nolan@tyndall.ie en
dc.identifier.articleid 415501
dc.relation.project info:eu-repo/grantAgreement/EC/FP7::SP1::NMP/604296/EU/Catalytic Partial Oxidation of Bio Gas and Reforming of Pyrolysis Oil (Bio Oil) for an Autothermal Synthesis Gas Production and Conversion into Fuels/BIOGO-FOR-PRODUCTION en


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