Grain boundary structure and current-voltage (I-V) characteristics were investigated for Nb-doped SrTiO3 bicrystals having small angle tilt boundaries with misorientation angles of 2° and 4° against . The bicrystals were fabricated by using hot-joining technique at 1400°C for 10 h under a pressure of 0.4 MPa. High resolution transmission electron microscopy study revealed that the joined boundaries are free from any secondary phases such as amorphous phases even on an atomic scale. The structures of the two boundaries are composed of edge type dislocations whose Burgers vector is . But the density of boundary dislocations differs between the two boundaries. They exist at an interval of 10 nm in the 2°-boundary and 5.2 nm in the 4°-boundary. On the other hand, it was found that non-linearity in I-V relation across the boundary increases with an increase in the misorientation angle. This result clearly indicates that the potential barrier height is closely related to the density of boundary dislocations in the case of small angle type boundaries.
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