Investigation of IrO2/SnO2 thin film evolution by thermoanalytical and spectroscopic methods

The formation mechanism of thermally prepared IrO2/SnO2 thin films has been investigated under in situ conditions by thermogravimetry combined with mass spectrometry (TG-MS) and infrared emission spectroscopy (IRES). Mixtures of varying composition of the precursor salts (SnCl2.2H(2)O dissolved in ethanol and IrCl3.3H(2)O dissolved in isopropanol) were prepared onto titanium metal supports. Then the solvent was evaporated and the gel-like films were heated in an atmosphere containing 20% O-2 and 80% Ar to 600degreesC. The thermogravimetric curves showed that the evolution of the oxide phases take place in several decomposition stages and the final mixed oxide film is formed between 490 and 550degreesC, depending on the noble metal content. Mass spectrometric ion intensity curves revealed that below 200degreesC crystallization water, residual solvent, and hydrogen-chloride (formed as a result of an intramolecular hydrolysis) are liberated. The decomposition of surface species (surface carbonates, carbonyls and carboxylates) formed via the interaction of the residual solvent with the precursor salts takes place up to 450degreesC as evidenced by emission Fourier transform infrared spectrometry.