Abstract
Local structures of the rhombohedral, orthorhombic, and tetragonal phases of barium titanate （BaTiO3）have been investigated using convergent-beam electron diffraction （CBED）. Nanometer sized rhombohedral structures have been found in both the orthorhombic and tetragonal phases. This indicates the existence of an order-disorder character in their phase transformations. The nanostructures in these phases are discussed in terms of an order-disorder model with off-centered Ti in the ［111］ directions. Spatial distributions of the nanostructures were examined by the combined use of the scanning transmission electron microscopy and convergent-beam electron diffraction methods （STEM-CBED method）. Two-dimensional structural fluctuations were successfully visualized in the tetragonal phase of BaTiO3.
