Processing of anatase prepared from hydrothermally treated alkoxy-derived hydrous titania

Spherical, submicrometre, amorphous hydrous titania powder synthesized by controlled hydrolysis and polymerization from titanium tetraethoxide solutions was hydrothermally converted to spherical polycrystalline anatase particles by autoclaving or refluxing. Green compacts produced with either autoclaved or refluxed powder via a colloid filtration route had a high density and were crack-free; processing with untreated hydrous titania resulted in cracked green compacts. Compacts of the hydrothermally treated powders could be sintered to 98% theoretical density at temperatures as low as 900° C. A compact of commercial powder produced in the same fashion was not observed to densify at such temperatures. Using various firing techniques, compacts of the hydrothermally treated powder could be sintered to 98% theoretical density or greater while controlling the titania phase assemblage as (1) anatase, (2) rutile, or (3) a mixture of anatase and rutile. By scaling the phase transformation and sintering kinetics, the grain size of the sintered microstructure can be controlled from a submicrometre to a micrometre scale.