Non-linear current-voltage property across Σ5(210) symmetric tilt boundary in Nb-doped SrTiO₃ bicrystal

Grain boundary structure and current-voltage (I-V) characteristics were investigated for Σ5(210) symmetrical tilt boundary of a Nb-doped SrTiO₃ bicrystal. The bicrystal was prepared by a hot-joining technique at high temperature in air. The high resolution transmission electron microscopy (HRTEM) study has revealed that the grain boundaries were perfectly joined at an atomic level without intergranular phases such as amorphous or secondary precipitates. In spite of the high coherency, the boundary tends to be faceted with low index planes of (110) and (410) to reduce grain boundary energy. On the other hand, the I-V property across the boundary was found to exhibit a cooling rate dependency from annealing temperature. In addition, the dependency shows a peak against cooling rates. This fact suggests that the non-linearity in I-V relation is dominantly controlled by a non-equilibrium process of a defect reaction.