Optimizing TiO₂ through Water-Soluble Ti Complexes as Raw Material for Controlling Particle Size and Distribution of...

Barium titanate (BaTiO₃) nanocubes with a narrow particle size distribution were synthesized using a three-step approach. First, a water-soluble Ti complex was synthesized using a hydrolysis method. Next, the titanium dioxide (TiO₂) raw material was synthesized via a hydrothermal method using various water-soluble titanium (Ti) complexes. The TiO₂ exhibited various particle sizes and crystal structures (anatase, rutile, or brookite) depending on the water-soluble Ti complex and the hydrothermal conditions used in its synthesis. Finally, BaTiO₃ nanocubes were subsequently created through a hydrothermal method using the synthesized TiO₂ particles and barium hydroxide octahydrate [Ba(OH)₂·8H₂O] as raw materials. The present study clarifies that the particle size of the BaTiO₃ nanocubes depends on the particle size of the TiO₂ raw material. BaTiO₃ particles with a narrow size distribution were obtained when the TiO₂ particles exhibited a narrow size distribution. We found that the best conditions for the creation of BaTiO₃ nanocubes using TiO₂ involved using lactic acid as a complexing agent, which resulted in a particle size of 166 nm on average. This particle size is consistent with an average of the width of the cubes measured from corner to corner diagonally, which corresponds to a side length of 117 nm. In addition, surface reconstruction of the BaTiO₃ was clarified via electron microscopy observations, identifying the outermost surface as a Ti layer. Electron tomography using high-angle annular dark-field (HAADF)-scanning transmission electron microscopy (STEM) confirmed the three-dimensional (3D) structure of the obtained BaTiO₃ nanocubes.