THERMOANALYTICAL INVESTIGATION ON THE FORMATION OF IRO2-BASED MIXED-OXIDE COATINGS

The formation reactions of IrO2/TiO2 mixed oxide films supported on ti tanium metal plate were followed by thermoanalytical (simultaneous TGA , DTG, DTA) and combined thermoanalytical-mass spectrometric (TGA-MS) techniques. The electrochemical characterization of the fired coatings was made by cyclic voltammetry. The thermal decomposition of the tita nium precursor salt, titanium diisopropoxide bis-2,4-pentanedionate, s hows a major change in the presence of hydrated iridium (III) chloride . Due to the catalytic effect of the added noble metal, an almost comp lete conversion of the organic components of the precursor mixture to CO2 and H2O is observed in the combustion stage. Chlorine, from therma l decomposition of the iridium salt, is produced in a separate stage a t higher temperatures, indicating that a sequence of steps occurs prio r to the oxide formation. For iridium chloride alone a complexation be tween the metal ion and the solvent (isopropanol) is observed, leading eventually to H2O and CO2 production (combustion step) between 300 an d 500-degrees-C. The cyclic voltammetry results indicate that the feat ures of the precursor reaction affect the charge storage capacity of t he oxide films.