(188ab) Distribution of Ti Atoms in Sn1-XTixO2 Solid Solutions

Metal oxide semiconductors with a rutile-phase such as TiO₂ and SnO₂ have been largely studied in the past due to their wide range of applications. For example, TiO₂ is used as white pigment, UV-shield in sun creams, photo catalyst and in solar cells. Pure or doped SnO₂, on the other hand, is employed as transparent isolating material, transparent conductive oxide (TCO) and it is the most utilized metal oxide for chemical gas sensing. In all of these applications the surface properties of the oxides play a major role. For instance, the adsorption of hydroxyl groups is directly correlated with the poor reliability of SnO₂-based sensors in the presence of variable relative humidity. Recently, it has been shown that this major shortcoming can be overcome by co-synthesis of another oxide such as TiO₂.[1] In fact, flame spray synthesis of the latter led to formation of Sn_1-xTi_xO₂ solid solutions with controlled surface properties and high sensitivity (e.g. to EtOH). However, the understanding of the synthesis process and the resulting formation of rutile lattice is still in progress. Using density functional theory (DFT) within the Gaussian and Plane Wave (GPW) formalism, rutile (110) surfaces of Ti-doped SnO₂ have been studied and compared to pure TiO₂ and SnO₂ surfaces. [2] The stability of surfaces with homogeneously distributed Ti atoms in the whole crystal was compared to that obtained with surface localized ones. Furthermore, accumulations of Ti-impurities in the SnO₂ bulk structure have been investigated including their effect on the rutile cell lattice constants (a and c) and on the formation energy .[3]

[1] Tricoli, A.; Righettoni, M.; Pratsinis, S. E. Nanotechnology 2009, 20, 315502. [2] Bandura, A. V.; Kubicki, J. D.; Sofo, J. O. J. Phys. Chem. B 2008, 112, 11616. [3] Camargo, A. C.; Igualada, J.A.; Beltrán, A.; Llusar, R.; Longo, E.; Andrés, J. Chem. Phys. 1996, 212, 381.