Abstract: Effects of sulfate ions and hydrolytic temperature on the TiCl₄-derived TiO₂ powders properties were investigated in detail. At 20℃, as-prepared
powder is amorphous and with huge specific surface area, its average pore diameter is in the mesoporous range. In the presence of a small amount of SO₄^2-,
pore diameter distribution is in more narrow range from 2nm to 5nm. Nanocrystalline TiO₂ powders can be prepared by raising the hydrolytic temperature, at 70℃
and in the presence of SO₄^2-, the as-prepared powder is pure anatase, however, in the absence of SO₄^2-, as-prepared powder is a mixture in both phases.
These nanocrystalline TiO₂ powders have high specific surface area (as high as 380 m²/g) and also are in ultrafine size (3.5nm) compared with alkoxide-derived TiO₂
powders. The properties of these powders were characterized by XRD,TEM, DRS and BET techniques.

Key words: nanocrystalline, titania, anatase, rutile, TiCl₄ hydrolysis