The thermal evolution process of IrO2-Ta2O5/Ti coatings with varying noble metal content has been investigated under in situ conditions by thermogravimetry combined with mass spectrometry. The gel-like films prepared from alcoholic solutions of the precursor salts (IrCl3.3H(2)O and TaCl5) onto titanium metal support were heated in an atmosphere containing 20% O-2 and 80% Ar up to 600degreesC. The liberation of the chlorinated species followed by the mass spectrometric ion intensity curves showed that the two oxide phases do not develop independently.The cracking of retained solvent, the combustion of organic surface species formed (and elemental carbon trapped in the film) was also followed by the MS curves. The formation of carbonyl- and carboxylate-type surface species connected to the noble metal were identified by Fourier transform infrared emission spectroscopy (IRES). These secondary processes-catalyzed by the noble metal-play an important role in the development of surface morphology of the films when used as anode materials in oxygen evolution reactions. (C) 2003 Elsevier B.V. All rights reserved.