Defect chemistry of Ti and Fe impurities and aggregates in Al 2 O 3

Jessica K. Bristow, Davide Tiana, Stephen C. Parker, Aron Walsh

Research output: Contribution to journalSpecial issue

11 Citations (Scopus)
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Abstract

We report a theoretical evaluation of the properties of iron and titanium impurities in sapphire (corundum structured α-Al2O3). Calculations using analytical force fields have been performed on the defect structure with the metals present in isolated, co-doped and tri-cluster configurations. Crystal field parameters have been calculated with good agreement to available experimental data. When titanium and iron are present in neighbouring face and edge-sharing orientations, the overlap of the d-orbitals facilitates an intervalence charge transfer (FeIII/TiIII → FeII/TiIV) with an associated optical excitation energy of 1.85 eV and 1.76 eV in the respective configurations. Electronic structure calculations based on density functional theory confirm that FeIII/TiIII is the ground-state configuration for the nearest-neighbour pairs, in contrast to the often considered FeII/TiIV pair. Homonuclear intervalence charge transfer energies between both FeIII/FeII and TiIV/TiIII species have also been calculated, with the energy lying in the infra-red region. Investigation of multiple tri-clusters of iron and titanium identified one stable configuration, TiIII–(TiIV/FeII), with the energy of electron transfer remaining unchanged.
Original languageEnglish
Pages (from-to)6198-6208
Number of pages11
JournalJournal of Materials Chemistry A
Volume2
Issue number17
Early online date5 Feb 2014
DOIs
Publication statusPublished - 7 May 2014

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Titanium
Iron
Aluminum Oxide
Impurities
Defects
Charge transfer
Corundum
Excitation energy
Photoexcitation
Defect structures
Sapphire
Ground state
Electronic structure
Density functional theory
Metals
Infrared radiation
Crystals
Electrons

Cite this

Defect chemistry of Ti and Fe impurities and aggregates in Al 2 O 3. / Bristow, Jessica K.; Tiana, Davide; Parker, Stephen C.; Walsh, Aron.

In: Journal of Materials Chemistry A, Vol. 2, No. 17, 07.05.2014, p. 6198-6208.

Research output: Contribution to journalSpecial issue

Bristow, Jessica K. ; Tiana, Davide ; Parker, Stephen C. ; Walsh, Aron. / Defect chemistry of Ti and Fe impurities and aggregates in Al 2 O 3. In: Journal of Materials Chemistry A. 2014 ; Vol. 2, No. 17. pp. 6198-6208.
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AB - We report a theoretical evaluation of the properties of iron and titanium impurities in sapphire (corundum structured α-Al2O3). Calculations using analytical force fields have been performed on the defect structure with the metals present in isolated, co-doped and tri-cluster configurations. Crystal field parameters have been calculated with good agreement to available experimental data. When titanium and iron are present in neighbouring face and edge-sharing orientations, the overlap of the d-orbitals facilitates an intervalence charge transfer (FeIII/TiIII → FeII/TiIV) with an associated optical excitation energy of 1.85 eV and 1.76 eV in the respective configurations. Electronic structure calculations based on density functional theory confirm that FeIII/TiIII is the ground-state configuration for the nearest-neighbour pairs, in contrast to the often considered FeII/TiIV pair. Homonuclear intervalence charge transfer energies between both FeIII/FeII and TiIV/TiIII species have also been calculated, with the energy lying in the infra-red region. Investigation of multiple tri-clusters of iron and titanium identified one stable configuration, TiIII–(TiIV/FeII), with the energy of electron transfer remaining unchanged.

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