Effect of Sn-precursor on the morphology and composition of Ir0.3Sn0.7O2 oxide films prepared by sol–gel process

With the aim of investigating the effect of the type of Sn-precursor on the physical-chemistry properties of iridium dioxide coatings, electrodes of Ir0.3Sn0.7O2 nominal composition were prepared by the sol–gel technique as an alternative to the classical thermal procedure. The influence of the Sn-precursor on the surface properties of these electrode materials was investigated by scanning electron microscopy, energy-dispersive X-ray and X-ray diffraction and cyclic voltammetry. The colloidal dispersion was prepared by refluxing (46 h, 80°C) a mixture in the appropriate proportion of precursors. Oxide films were deposited on Ti-subtracts by thermal decomposition (400°C, 1h, 5 l min−1 O2 flux) of colloidal dispersion. An expressive difference was observed in the morphology of the oxide layer with the change of the type of Sn-precursor. The X-ray diffractogram of the SnCl2-precursor film had only broad peaks indicating the amorphous state of the oxide mixture. While the [CH3(CH2)3]3SnOC2H5-precursor film had diffraction peaks due to SnO2 rutile structure and reflections due to iridium metal in addition to Ir hydroxyoxide phase. The cyclic voltammetric data are consistent with the surface analysis results. Independently of the Sn-precursor adopted, the actual composition of the layer is close to nominal showing the sol–gel procedure is more efficient than the thermal decomposition procedure to obtain Sn containing with this property.