Anisotropic Assembly during Heat‐Up: The Early Stage Hydrothermal Synthesis of TiO₂ from a Complexed Precursor

Abstract Hydrothermal synthesis is a widely used technique for the production of TiO₂ in various shapes in several industries. In the hydrothermal synthesis of TiO₂ from a complexed precursor, the processes that occur during the heat‐up phase are not fully understood, especially those factors that affect the size and morphology of crystals. Here we report an in situ small angle x‐ray scattering analysis to gain insights into the mechanism of early‐stage hydrothermal synthesis of TiO₂ from a complexed precursor. We observed that the precursor molecules form elongated cuboid‐like shapes before they assemble and form the crystal nucleus. One of the edges grows with an exponential behaviour as a function of temperature, while the other two edges remain small. In the following stage, the precursor rods form a characteristic association with a fractal dimension of 2.0 to 2.2. In this stage small particles start to form very slowly within the preformed structures.