Compensation Effect in Semiconducting Barium Titanate

Donor-doped, stoichiometric BaTiO₃ sintered at 1350°C for 1 h exhibits a maximum room-temperature conductivity at La³⁺]～0.15 mol%. Elements of lower valence than Ba²⁺ or Ti⁴⁺, when incorporated into semiconducting BaTiO₃, are regarded as poisoning impurities, i.e., acceptors. They tend to increase the room-temperature resistivity of the semiconducting BaTiO₃. For insulating BaTiO₃ resulting from high Mg²⁺ acceptor doping levels, the semiconductivity can be restored by introducing higher La³⁺ donor-dopant concentrations. This behavior is interpreted as a compensation effect based on the defect chemistry of the acceptor- and donor-doped BaTiO₃.