Transition of Compensating Defect Mode in Niobium‐Doped Barium Titanate

The influence of Nb‐doping from 1.0 to 8.0 at.% on grain size, ferroelectric phase transition, lattice strain, and electrical properties of BaTiO 3 Cerumics has been studied. A change in the Nb‐doping effect was observed at compositions around 3.5–4.5 at.% Nb. The impedance behavior revealed that specimens of low Nb‐doping had an activation energy of 1.85 eV for carrier conduction either in bulk or at grain boundaries, but specimens having a high Nb‐doping content showed an energy of 1.30 eV in bulk and 1.85 eV at grain boundaries. The capacitance–voltage relation also disclosed different influences of Nb‐doping on the potential barrier height at grain boundaries. The above results are explained by the transition of a compensating defect mode from pure barium vacancies to a combination of titanium vacancies in grain interiors and barium vacancies at grain boundaries as the Nb‐doping content in BaTiO 3 is increased.