Optimizing TiO 2 through Water-Soluble Ti Complexes as Raw Material for Controlling Particle Size and Distribution of Synthesized BaTiO 3 Nanocubes.

Barium titanate (BaTiO 3 ) 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 (TiO 2 ) raw material was synthesized via a hydrothermal method using various water-soluble titanium (Ti) complexes. The TiO 2 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, BaTiO 3 nanocubes were subsequently created through a hydrothermal method using the synthesized TiO 2 particles and barium hydroxide octahydrate [Ba(OH) 2 ·8H 2 O] as raw materials. The present study clarifies that the particle size of the BaTiO 3 nanocubes depends on the particle size of the TiO 2 raw material. BaTiO 3 particles with a narrow size distribution were obtained when the TiO 2 particles exhibited a narrow size distribution. We found that the best conditions for the creation of BaTiO 3 nanocubes using TiO 2 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 BaTiO 3 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 BaTiO 3 nanocubes.