Abstract
We report a theoretical evaluation of the properties of iron and titanium impurities in sapphire (corundum structured α-Al2O 3). 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/Ti III → 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 Ti IV/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-(Ti IV/FeII), with the energy of electron transfer remaining unchanged. This journal is
Original language | English |
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Pages (from-to) | 6198-6208 |
Number of pages | 11 |
Journal | Journal of Materials Chemistry A |
Volume | 2 |
Issue number | 17 |
DOIs | |
State | Published - 7 May 2014 |