Thermodynamic calculations were used to estimate the free energy for reactions of anatase and TiO2.nH(2)O with K2CO3 to generate potassium dititanate at 25-1200degreesC, and the results showed that amorphous TiO2.nH(2)O with reaction activity higher than that of anatase can decrease the lowest generation temperature of potassium dititanate. The precise temperatures of 300degreesC for TiO2.nH(2)O and 500degreesC for anatase were determined by experiments. The crystal growth of potassium dititanate was studied experimentally. It was found that potassium dititanate hydrate is first formed from TiO2.nH(2)O at 300degreesC, and converts into K2Ti2O5.0.35H(2)O at 640degreesC The dehydration of K2Ti2O.0.35H(2)O occurs at 660-820degreesC, ending with the generation of K2Ti2O5 single crystals at 820degreesC Potassium dititanates with a diversity of morphologies, sizes, water contents, and crystallinities, showing various abilities for optical absorption/reflex, were fabricated from TiO2.nH(2)O under control, whereas only K2Ti2O5 was prepared from anatase at 500-850degreesC, which indicate that reaction processes and properties of products are determined according to the type of reactants and the reaction temperature. (C) 2004 American Institute of Chemical Engineers AIChE J, 50: 1568-1577, 2004