Low‐temperature controllable calcination syntheses of potassium dititanate

Thermodynamic calculations were used to estimate the free energy for reactions of anatase and TiO 2 · n H 2 O with K 2 CO 3 to generate potassium dititanate at 25–1200°C, and the results showed that amorphous TiO 2 · n H 2 O with reaction activity higher than that of anatase can decrease the lowest generation temperature of potassium dititanate. The precise temperatures of 300°C for TiO 2 · n H 2 O and 500°C 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 TiO 2 · n H 2 O at 300°C, and converts into K 2 Ti 2 O 5 ·0.35H 2 O at 640°C. The dehydration of K 2 Ti 2 O 5 ·0.35H 2 O occurs at 660–820°C, ending with the generation of K 2 Ti 2 O 5 single crystals at 820°C. Potassium dititanates with a diversity of morphologies, sizes, water contents, and crystallinities, showing various abilities for optical absorption/reflex, were fabricated from TiO 2 · n H 2 O under control, whereas only K 2 Ti 2 O 5 was prepared from anatase at 500–850°C, which indicate that reaction processes and properties of products are determined according to the type of reactants and the reaction temperature. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1568–1577, 2004