Low-temperature controllable calcination syntheses of potassium dititanate

Thermodynamic calculations were used to estimate the free energy for reactions of anatase and TiO₂·nH₂O with K ₂CO₃ to generate potassium dititanate at 25-1200°C, and the results showed that amorphous TiO₂·nH₂O with reaction activity higher than that of anatase can decrease the lowest generation temperature of potassium dititanate. The precise temperatures of 300°C for TiO₂·nH₂O 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 TiO₂·nH₂O at 300°C, and converts into K₂Ti₂O₅·0.35H₂O at 640°C. The dehydration of K₂Ti₂O₅·0. 35H₂O occurs at 660-820°C, ending with the generation of K ₂Ti₂O₅ 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 TiO₂·nH₂O under control, whereas only K₂Ti₂O₅ 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.