The crystalline phase stability of titania particles prepared at room temperature by the sol-gel method

Titania particles having anatase, brookite and rutile phase were prepared a t various H+/TTIP (Titaniumtetraisopropoxide) mole ratios and room temperat ure by the sol-gel method. The crystalline phases according to the variatio n of the post heat treatment temperature were observed. The crystalline pha se and the phase transformation, morphology, and crystallite size were iden tified by using XRD, TG/DTA, Raman spectroscopy and TEM. The brookite phase of titania particles prepared at the H+/TTIP mole ratio of 0.02 and room t emperature was not transformed into anatase or rutile even with the heat tr eatment at 750 degreesC, and also the anatase phase was stable at the tempe rature as high as 850 degreesC. However, the titania particles prepared at the H+/TTIP mole ratio of 0.67, which contained the mixed phases of anatase , brookite, and rutile at room temperature, showed only rutile phase at tem perature of 750 degreesC. It was thus shown that the initial crystalline ph ase of the primary particles prepared at room temperature had an important effect on the phase transformation behavior upon post heating. Phase transf ormation from brookite to anatase and subsequently to rutile occurred with heating. (C) 2001 Kluwer Academic Publishers.