Hot-water treatment of sol-gel derived SiO sub(2)-TiO sub(2) microparticles and application to electrophoretic deposition for thick films

SiO sub(2)-TiO sub(2) spherical microparticles of about 0.7 mu m in diameter were prepared by the sol-gel method. Anatase nanocrystals were formed in the microparticles and their specific surface area was increased after a hot-water treatment at 90 degree C. From the changes in the concentration of I sub(2) photocatalytically generated from KI aqueous solution, the activity of the SiO sub(2)-TiO sub(2) microparticles was found to increase with increasing the hot-water treatment time. Particulate, thick films were electrophoretically deposited on indium tin oxide (ITO)-coated glass substrates using the anatase nanocrystal-precipitated SiO sub(2)-TiO sub(2) microparticles. The thickness of the electrophoretically deposited particulate film increased to be approximately 10 mu m with an increase in applied voltage. The resultant thick film showed a high photocatalytic activity.