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

The differences of the binding energy of the Ti 2p(3/2) electron obrained b y X-ray photoelectron spectroscopy (XPS) in ternary spinels such as LiFeTiO 4, LiMnTiO4 and LiCrTiO4 have bren studied. X-ray diffraction patterns for these spinels and neutron powder diffraction data for LiFeTiO4, LiMnTiO4 an d 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) ca tions are distributed 100% in octahedral sites for LiFeTiO4. 66% in octahed ral sites and 34% in tetrahedral sites for LiMnTiO4, and 88% in octahedral sites and 12% in tetrahedral sites for LiFeTiO4. XPS studies confirm the ox idation state of the cations Fe(III), Cr(III), Mn(III) and Ti(IV); and usin g 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%) ass igned to octahedral and tetrahedral Ti(IV), respectively for LiMnTiO4. In t he 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 observ ed 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.