Preparation and characterisation of high surface area stannic oxides:: structural, textural and semiconducting properties

Nanosized cassiterite-type samples have been prepared following two different methods: nitric acid attack on metallic tin and neutralisation of SnCl4 solution by hydrazine. Samples have been characterised by different physico-chemical techniques (X-ray diffraction (XRD), isotherm measurements of N-2 adsorption-desorption, scanning electronic microscopy (SEM), FTIR and UV-VIS spectroscopy). Structural, textural and semi-conductive proper-ties have been thus investigated and their evolution as a function of the temperature of calcination in flowing oxygen up to 600 degreesC has been studied. The progressive formation of oxygen vacancies. leading to non-stoichiometric SnO2, was observed during this treatment for both samples. An important feature is that, after this treatment, no oxygen vacancies could be observed at the crystallites surface, their formation requiring specific treatments like outgassing at high temperatures. Strong differences in textural properties. types of surface hydroxyl species and concentration of oxygen vacancies at the crystallites surface have been also evidenced between the two samples. (C) 2002 Elsevier Science B.V. All rights reserved.