Hole conduction and nonlinear current–voltage behavior in multiferroic lanthanum-substituted bismuth ferrite

Abstract Polycrystalline Bi1−xLaxFeO3 (BLF, x = 0.05–0.2) were prepared by solid state reaction and followed by annealing in O2, air and N2. The electrical properties of BLF ceramics were investigated by impedance spectroscopy and it is found that the conduction is dominated by p-type conduction. The conductivity of samples varies by several orders of magnitude, depending on the oxygen partial pressure during the annealing process. Activation energy (Ea) increases from ∼0.5 eV for O2/air-annealed samples to ∼0.9 eV for the N2-annealed samples, and Ea shows a slightly increase with the increment of La doping amount. Besides, all the samples exhibit nonlinear current (I)–voltage (V) characteristics, and the threshold field voltage is much higher for the N2-annealed samples than for the O2-annealed samples. The nonlinear coefficient increases with the increase of oxygen partial pressure and temperature as well as the decrease of the La doping amount. The intrinsic electrostatic barrier at the domain walls rather than grain boundaries is responsible for the nonlinear behavior.