Electrical conductivity–defect structure correlation of variable-valence and fixed-valence acceptor-doped BaTiO3 in quenched state

Abstract

Insulation resistance degradation of dielectric BaTiO₃ is expected to be closely correlated to its defect structure frozen in from elevated processing temperatures. For BaTiO₃, respectively doped with variable-valence (Mn_Ti) and fixed-valence acceptors (Al_Ti), their defect structures were frozen in by quenching at different equilibrium oxygen activities in the range of −18 < log a_O2≤ 0 at 1000 and 900 °C, respectively, and their electrical conductivities were measured against temperature in the range of 200 ≤T/K ≤ 494 by impedance spectroscopy. Frozen-in defect structures were calculated and compared with the conductivity as measured in the quenched state. A close correlation has been confirmed between the bulk conductivity as measured in the quenched state and the frozen-in defect structure as calculated. The effects of variable- and fixed-valence acceptor impurities on the defect structure and electrical conductivity in the quenched state are highlighted in the light of hole trapping, and the charge transport behavior in the quenched state is discussed.