DOPANTS IN VAPOR-PHASE SYNTHESIS OF TITANIA POWDERS

Gas-phase synthesis of titania by TiCl4 oxidation in the presence of dopants (SiCl4, POCl3, and BCl3) was investigated in an aerosol reactor as a function of temperature (1300-1700 K) and dopant concentration (0-25 mol% of TiCl4). The addition of dopants, most notably silicon and phosphorus, drastically altered the morphology of titania particles from polyhedral to spheroidal, increased the extent of aggregation, increased the specific surface area, reduced the primary particle size, and decreased the rutile content. The observed morphology/crystallinity changes were explained in terms of ionic radii and valence of the dopant element.