Comparative evolved gas analyses of crystalline and amorphous titanium(IV)oxo-hydroxo-acetylacetonates by TG-FTIR and TG/DTA-MS

Decomposition of crystalline and amorphous titanium(IV)oxo-acetylacetonate chemicals have been studied in situ up to 800 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR) for the analysis of evolved gases (EGA) in order to get more information about pyrolytic processes taking place at elevated temperatures during smooth TiO2 layer processing. Crystalline samples (characterized by XRD, PDF 00-35-1778 reference pattern) are releasing acetylacetone (acacH) vapors already from 140 °C onwards. At 245 °C, after an acceleration of this release process, a huge and sharp exothermic heat effect also occurs and results in additional evolution of acetic acid, CO2, H2O, and CO. Minute amount of unidentified volatile species with ion fragments not higher than m/z = 152 are also detected up to 285 °C. The remaining organic residues are burning out from the solid phase in two further exothermic stages until 500 °C. While an amorphous hydrated sample (with low acetylacetonate content) releases first 6.6% of water vapor until 140 °C, then acetone and acetylacetone up to 300 °C. Between 215 and 385 °C, some acetic acid, CO2, and CO is also evolved. Formation of CO2 is detected till 650 °C. At 800 °C, the anatase: rutile TiO2-ratio were 11:89 and 84:16 for the well-crystallized and the amorphous sample, respectively.