Sol-Gel Processing of Bi(2)Ti(2)O(7) and Bi(2)Ti(4)O(11) Films with Photocatalytic Activity

A new sol-gel synthesis based on chloride compounds as precursors has been used to prepare bismuth titanate (BT) films. The films have been deposited by dip-coating and fired at different temperatures in air; they remain amorphous up to 500 degrees C, and crystallize into the pyrochloric cubic phase Bi(2)Ti(2)O(7) between 600 degrees and 700 degrees C while at higher temperatures of firing the stable Bi(2)Ti(4)O(11) monoclinic phase is formed. The films have been characterized by X-ray diffraction analysis at gracing incidence, X-ray photoelectron spectroscopy, ellipsometric spectroscopy, UV-visible absorption, and atomic force microscopy. The photocatalytic properties of the films have been evaluated by exposing a methyl orange solution containing the BT films to UV light. The test has shown that the Bi(2)Ti(2)O(7) films have a higher activity in comparison with reference anatase titania films.