Effect of fluorine doping on the properties of tin oxide based powders prepared via Pechini's method

Surface modification of ceramic powders is an important method to change and control the properties of the material. Grain size, surface charge density and consequently the powder-surroundings interfacial proper-ties can be modified by the use of additives. The surface properties Of SnO2-based powders doped with F, prepared via an organic chemical route derived from Pechini's method, was studied using infrared spectroscopy (FT-IR), surface area determination, X-ray diffraction (XRD), dynamic electrophoretic mobility and thermogravimetric analysis. The results showed that there is an F saturation concentration (5 mol%), above which, the surface characteristics of the powder became constant. Compared to the pure SnO2, addition of F to the oxide results in a powder that has a greater surface area. Water suspensions of the powder presents an interface that is acidic (isoelectric point = 3.31) and more hydrophobic. Furthermore, F-doped SnO2 presents different types of adsorption sites for water adsorption. All the results constitute strong arguments supporting the additives surface segregation model, detrimental to the theory of solid solution formation. (C) 2004 Elsevier B.V. All rights reserved.