The gel route to Cr 3+-doped TiO 2, an ESR study

Abstract

Cr 3+ ions have been incorporated as Cr(acac) 3 to the titanium alkoxide precursor in order to follow hydrolysis and polycondensation by ESR. X-band and Q-band spectra have been recorded and analyzed all the way from the molecular precursors to the rutile TiO 2 , giving detailed information about the different steps involved in the sol-gel process. Our experiments show that a mixed Cr-Ti alkoxide is obtained upon mixing and heating the molecular solution. They also point out the role of acetate as ligands chemically involved in the process. No modification is observed during the gel-xerogel transformation and short range order in the amorphous xerogel appears to be completely different than in TiO 2 crystalline phases. Upon heating anatase and then rutile are successively obtained.