Thermochemical formation of IrO2 and Ir

Formation of IrO2 and Ir by thermal decomposition of iridium(III)-acetylacetonate and IrO2 from iridium(IV)-oxide dihydrate has been investigated by XRD, thermal analysis, FT-IR and laser Raman spectroscopy. Iridium(III)-acetylacetonate decomposed in air at 200 jC, yielding Ir and traces of IrO2. An increase in heating temperature led to an increase in IrO2 fraction. A gradual increase in crystallite size of Ir from 11(3) to 30(7) nm with the increase of temperature from 200 to 550 jC was measured, whereas the crystallite size of IrO2 changed from 12(4) to 20(5) nm in the range between 350 and 550 jC. Ir film formed at 550 jC contained crystallites of several tens of nanometers. Iridium(IV)-oxide dihydrate showed an amorphous XRD pattern. Upon heating in air at 600 jC for 2– 24 h, crystalline IrO2 as a single phase was produced. Broad IR band at f550 cm 1 was recorded due to m(Ir– O) vibrations. Raman spectrum of IrO2 2H2O showed two broad bands at 708 and 744 cm 1, which could be assigned to IrO2. An additional broad band at 352 cm 1 was also visible. The nature of Raman band at 352 cm 1 was interpreted in terms of poor crystallinity and/or the presence of very fine IrO2 particles that may tend to periodic aggregation. IrO2 produced at 600 jC showed Raman bands at 718 and 544 cm 1. These wave numbers are smaller than those observed for IrO2 single crystal.