Crystallization of Al₂O₃-TiO₂ sol-gel systems

Al₂O₃-TiO₂ thin films and powders were synthesised from acid catalyzed sols of aluminium and titanium alkoxides containing acetyl acetone as a chelating agent. The crystallization of the system was studied as a function of the relative compositions and the firing temperature. Films of four different alumina-titania compositions (10, 20, 30 and 40 mol % alumina) were prepared and fired at various temperatures in the range from 300 to 1000°C. The films and powders were amorphous, at any composition, up to about 600°C. Larger molar contents of Al₂O₃ were found to have an inhibitory effect on the crystallization of TiO₂, while larger contents of TiO₂ had only a weak influence on Al₂O₃ crystallization. The formation of a metastable ß-Al₂TiO₅ phase was observed in films at 1000°C.