NANOTWINS IN BATIO3 NANOCRYSTALS

BaTiO3 nanocrystals, in which the coexistence of the high-temperature hexagonal phase with the cubic-tetragonal phase at room temperature wa s suggested in a previous study, have been investigated using high-res olution transmission electron microscopy. The BaTiO3 nanocrystals were found to have the cubic-tetragonal structure with (111) planar defect s. The observed images other than cubic-tetragonal BaTiO3 showed first ly coherent (111) twins often forming lamellae consisting of three to five atomic layers, secondly periodic images of a 0.70 nm x 0.49 nm re ctangle and thirdly incoherent (111) planar images. The rectangular la ttice and the incoherent (111) planar images originated from the super imposition of the matrix and the (111) twin. The peaks that were ascri bed to the hexagonal phase in the electron diffraction pattern were we ll explained as a result of the nano-sized twins in the cubic-tetragon al matrix.