Microstructure and phase evolution of TiO2 precursors prepared by peptization-hydrolysis method using polycarboxylic acid as peptizing agent

Titanium dioxide precursors have been prepared by the peptization-hydrolysis process using titanium tetrachloride as the raw material and polycarboxylic acid as the peptizing agent. To avoid the aggregation of the original precursor particles, an anti-aggregating process is carried out after the hydrolysis by employing inorganic acids. FT-IR spectroscopy and elemental analysis indicate that a certain amount of residual dicarboxylic groups still remains in all TiO2 precursors and that the chemical composition of the precursors is nonstoichiometric. It is verified by Raman spectroscopy that all the precursors present a short-range ordered structure in the octahedral coordination of the titanium with oxygen cluster and the particle size is in nanometer scale. It is also found that the microstructure of the precursors is affected to some extent by the modification of inorganic acid. Anatase nanophase exists in all of the precursors which are obtained in the anti-aggregating process. Apart from the anatase nanophase, small amounts of amorphous nanosize titania particles are formed under a lower pH value (less than two) during the anti-aggregating period. The chelating effect may play an important role in the formation of anatase nanophase during the hydrolysis process in the preparation of titania precursor. XRD and Raman analysis show that all the precursors transformed into pure anatase after being sintered at around 300 degrees C. (C) 1998 Elsevier Science S.A. All rights reserved.