Dislocation loops observed in nonstoichiometric and stoichiometric (Ba,Ca)TiO 3 , and in stoichiometric BaTiO 3 sintered in a reducing atmosphere, were characterized by conventional transmission electron microscopy (TEM) under two-beam conditions and high-resolution TEM atomic structure analysis. Dislocation loops mostly lay on {100} planes with Burgers vectors of type ͗100͘. The dynamic behavior of these dislocation loops during the electron beam irradiation (EBI), however, was classified into two different types of dislocation loops: in A-site-excess (Ba,Ca)TiO 3 , contrasts of dislocation loops faded completely away; in BaTiO 3 and B-site-excess (Ba,Ca)TiO 3 , fine-line contrasts remained. Dislocation loops with Burgers vectors of type 1 ⁄2͗100͘ and the resultant crystallographic shear (CS) structure with a displacement vector of type 1 ⁄2͗110͘ after EBI were proposed to interpret residual line images. Disappearance of these line images in A-site-excess (Ba,Ca)TiO 3 strongly suggests preferential Ca ion site occupancy at the CS structure.
Nonstoichiometric 10-mol%-excess-BaO-BaTiO 3 (Ba 1.1 TiO 3.1 ) thin film grown on a (100) SrTiO 3 substrate consisted of heteroepitaxial c-axis-oriented BaTiO 3 perovskite crystals including Ruddlesden-Popper planar faults and nanometerscale multiple (111) twin lamellae. High-resolution electron microscopy and electron energy-loss spectroscopy revealed that nanotwins with coherent (111) ⌺3 coincident site lattice boundaries were terminated in the BaTiO 3 matrix to form incoherent (211) ⌺3 boundaries accommodating excess barium ions. Both Ruddlesden-Popper planar fault and incoherent (211) boundary formation were proposed as possible accommodation mechanisms of excess barium ions in the perovskite film.
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