Shape-Controlled Monocrystalline Ferroelectric Barium Titanate Nanostructures: From Nanotubes and Nanowires to Ordered Nanostructures

We report for the first time on the controlled hydrothermal synthesis of barium titanate nanostructures using Na2Ti3O7 nanotubes and nanowires as synthetic precursors. A variety of nanostructured BaTiO3 have been prepared, exhibiting either simple shapes of nanowires, nanosheets, nanocubes, and hexagonal nanoparticles or ordered architectures of coral-like nanostructures of assembled nanorods, starfish-like nanostructures, and sword-like nanostructures. The shapes of the various BaTiO3 products are found to be dependent on the concentration of Ba(OH)2, the temperature, and the nature of the precursors. The synthesis route exploits the differences in the hydrothermal stability of the Na2Ti3O7 nanotubes and nanowires and the temperature-dependent crystal structure of barium titanate. Various nanoblocks, including nanosheets and nanorods formed from the Na2Ti3O7 nanotubes and nanowires, respectively, grow and assemble to form the ordered BaTiO3 nanostructures. This represents a new approach that is capable of assembling ordered perovskite nanostructures using relatively large nanoblocks formed from layered alkali-metal titanates. The process offers more flexibility than those using inorganic titanium salts or organometallic titanium compounds, which commonly leads to the formation of only BaTiO3 nanoparticles.