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

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dc.check.date2018-09-05
dc.check.infoAccess to this article is restricted until 12 months after publication by request of the publisher.en
dc.contributor.authorCarey, John J.
dc.contributor.authorNolan, Michael
dc.contributor.funderSeventh Framework Programmeen
dc.contributor.funderScience Foundation Irelanden
dc.contributor.funderHigher Education Authorityen
dc.contributor.funderEuropean Cooperation in Science and Technologyen
dc.date.accessioned2017-09-11T09:04:18Z
dc.date.available2017-09-11T09:04:18Z
dc.date.issued2017-09-05
dc.date.updated2017-09-11T08:45:30Z
dc.description.abstractModification 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.sponsorshipEuropean Cooperation in Science and Technology (COST ACTION CM1104)en
dc.description.statusPeer revieweden
dc.description.versionAccepted Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.articleid415501
dc.identifier.citationCarey, 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/aa8250en
dc.identifier.doi10.1088/1361-648X/aa8250
dc.identifier.issn0953-8984
dc.identifier.issued41en
dc.identifier.journaltitleJournal of Physics: Condensed Matteren
dc.identifier.urihttps://hdl.handle.net/10468/4675
dc.identifier.volume29en
dc.language.isoenen
dc.publisherIOP Publishingen
dc.relation.projectinfo: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-PRODUCTIONen
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/aa8250en
dc.subjectDensity functional theoryen
dc.subjectCharge compensationen
dc.subjectNon classical mechanismen
dc.subjectChromium oxideen
dc.subjectMetal dopingen
dc.subjectVacancy formationen
dc.subject~Tyndall National Institute - Journal Articles~en
dc.titleNon-classical behaviour of higher valence dopants in chromium (III) oxide by a Cr vacancy compensation mechanismen
dc.typeArticle (peer-reviewed)en
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