Evolved Gas Analysis Investigation of the Reaction between Tris(2,4-pentanedionato)aluminum and Water Vapor in Chemical Vapor Deposition Processes To Produce Alumina

Evolved gas analysis−Fourier transform infrared spectroscopy was used to investigate the pyrolysis of tris(2,4-pentanedionato)aluminum on glass surfaces between 500 and 900 K in vacuum and in low-pressure water vapor atmospheres. Pyrolysis of tris(2,4-pentanedionato)aluminum in vacuum produced Al 2 O 3, carbon, water vapor, and several volatile organic products. This pyrolysis is surface enhanced and has an apparent activation energy of ∼100 kJ/mol. Water vapor reacted with the tris(2,4-pentanedionato)aluminum to form 2,4-pentanedione and Al 2 O 3 . Largely pure Al 2 O 3 was formed between 600 and 700 K in a water vapor atmosphere. This reaction was first order in the water vapor pressure. The order in tris(2,4-pentanedionato)aluminum was modeled well by the Langmuir adsorption isotherm. The apparent activation energy for the production of 2,4-pentanedione varied with the reaction conditions and had a lower limit of ∼28 kJ/mol when the reaction was run in excess water vapor. Possible reaction sequences are given for each case. The formation of Al(C 5 H 7 O 2 ) 2 OH is postulated to be a reaction intermediate during each sequence. This intermediate has not been isolated.