Ferroelectric Mesocrystalline BaTiO₃/SrTiO₃ Nanocomposites with Enhanced Dielectric and Piezoelectric Responses

A platelike mesocrystalline BaTiO 3 /SrTiO 3 (BT/ST) nanocomposite is prepared via a clever two-step solvothermal soft chemical process. First a protonated titanate H 1.07 Ti 1.73 O 4 · n H 2 O (HT) crystal with a layered structure and platelike morphology is solvothermally treated in a Ba(OH) 2 solution to generate a homogeneous platelike BaTiO 3 /HT (BT/HT) nanocomposite. Second the generated BT/HT nanocomposite is solvothermally treated in a Sr(OH) 2 solution to generate the mesocrystalline BT/ST nanocomposite with platelike particle morphology. The transformation reactions from the HT precursor to the mesocrystalline BT/ST nanocomposite are topochemical conversion reactions, and the formed BT/ST nanocomposite is constructed from well-aligned BT and ST nanocrystals in the same crystal-axis orientation. The BT/ST nanocomposite annealed at 900 °C shows a ferroelectric behavior and drastically enhanced piezoelectric and dielectric responses owing to the introduction of a lattice strain at a three-dimensional heteroepitaxial interface between the BT and ST nanocrystals in the mesocrystal. The nanostructure of the BT/ST mesocrystal is suitable for simultaneous application of the strain engineering and the orientation engineering to develop high performance piezoelectric and dielectric materials.