Hydrothermal Synthesis of Thin Films of Barium Titanate Ceramic Nano-Tubes at 200°C

A novel, low‐temperature synthesis method for producing BaTiO3 thin films patterned in the form of nano‐tubes (“honeycomb”) on Ti substrates is reported. In this two‐step method, the Ti substrate is first anodized to produce a surface layer (∼200–300‐nm thickness) of amorphous titanium oxide nano‐tube (∼100‐nm diameter) arrays. In the second step, the anodized substrate is subjected to hydrothermal treatment in aqueous Ba(OH)2, where the nano‐tube arrays serve as templates for their hydrothermal conversion to polycrystalline BaTiO3 nano‐tubes. This opens the possibility of tailoring the nano‐tube arrays and of using various precursor solutions and their combinations in the hydrothermal bath, to produce ordered, patterned thin‐film structures of various Ti‐containing ceramics. These could find use not only in a variety of electronic device applications but also in biomedical applications, where patterned thin films are also desirable.