Surface characterisation of spinels with Ti(IV) distributed in tetrahedral and octahedral sites

The differences of the binding energy of the Ti 2p(3/2) electron obrained by X-ray photoelectron spectroscopy (XPS) in ternary spinels such as LiFeTiO4, LiMnTiO4 and LiCrTiO4 have bren studied. X-ray diffraction patterns for these spinels and neutron powder diffraction data for LiFeTiO4, LiMnTiO4 and LiCrTiO4 reveal that Fe(III) is in octahedral and tetrahedral sites, and Cr(III) and Mn(III) are exclusively in octahedral sites. However. Ti(IV) cations are distributed 100% in octahedral sites for LiFeTiO4. 66% in octahedral sites and 34% in tetrahedral sites for LiMnTiO4, and 88% in octahedral sites and 12% in tetrahedral sites for LiFeTiO4. XPS studies confirm the oxidation state of the cations Fe(III), Cr(III), Mn(III) and Ti(IV); and using high resolution XPS (5.85 eV pass energy) it is possible to decompose the Ti 2p(3/2) signal in two peaks at 458.7 eV (68%) and at 458.7 eV (32%) assigned to octahedral and tetrahedral Ti(IV), respectively for LiMnTiO4. In the case of LiCrTiO4, the Ti 2p(3/2) signal could he decomposed in two peaks at 458.4 eV (87%) and 459.3 eV with a similar assignation than that observed for LiMnTiO4. A single Ti 2P(3/2) peak at 458.1 eV and corresponding to octahedral Ti(IV) was observed for LiFeTiO4. (C) 2001 Elsevier Science B.V. All rights reserved.