Abstract: Highly dispersed TiO2 nanometer powders with controlled structure were synthesized by chemical complex sol-gel auto-igniting process. The initial oxidant/reductant molar ratio, swelling of gel and temperature schedule were chosen as key variables for the controlled synthesis: by changing the initial oxidant/reductant molar ratio from 2 to 7, TiO2 having a particle size about 30 nm was obtained at 600 ℃ with a mass fraction of rutile ranging from 25％ to 68.2％; sufficient swelling and carbonizing of the gels at 150 ℃ removed non-bridging hydroxyl groups and broke down the hydrogen bonds between particles, so the formation of hard agglomerates was avoided; the mass fraction of rutile and particle size of TiO2 increased with increasing of calcination temperature; agglomerates of TiO2 were formed at 800 ℃. The optical absorption edges significantly shifted to longer wavelengths in the UV-Vis diffuse reflectance spectra of the as-prepared TiO2, and the reflectivity was about 10％ lower than that of commercial TiO2. It was found that the as-prepared TiO2 with the optimal rutile fraction of 55.5％ achieved the best optical absorption.

Key words: Sol-gel auto-igniting process, Titanium dioxide, Nanometer powder, 　Controlled synthesis