Kinetic Study on the Crystal Transformation of Fe-Doped TiO₂ via In Situ High-Temperature X-ray Diffraction and...

Titanium dioxide (TiO₂) is widely used in various major industries owing to its different crystal forms and functions. Therefore, fabricating suitable crystalline TiO₂ through reasonable processes is necessary. In this study, Fe-doped TiO₂ precursors were prepared via hydrolysis. Further, in situ high-temperature X-ray diffraction and transmission electron microscopy were used to transform the synthesized precursor in its crystal form. The Rietveld full-spectrum fitting method could accurately yield two different crystal forms at instant temperatures. Additionally, the rate relation between the crystal form transformation and reaction conditions was obtained. Results showed that the addition of Fe increased the temperature of phase transition of TiO₂ anatase to rutile and accelerated the anatase → rutile transformation process. Further, crystal phase transition kinetic analysis showed that the phase transition kinetic model of Fe-doped TiO₂ matched the Johnson-Mehl-Avrami-Kohnogorov (JMAK) model and that its phase transition was affected by crystal defects. Finally, Fe³⁺ in Fe-doped TiO₂ was reduced to Fe²⁺ to generate oxygen vacancies, thus promoting the rate of transformation from titanium ore to rutile.