Enhanced multiferroic properties of BiFeO3 ceramics by Ba and high-valence Nb co-doping

Bi0.8Ba0.2Fe1−xNbxO3 (BBFNx) ceramics with x=0, 0.015 and 0.025 were prepared by a modified Pechini method. The formation of the desired materials was confirmed using X-ray diffraction. Nb substitution effectively suppressed the spiral spin structure and enhanced the ferromagnetic moment. Substitution with Nb also improved the ferroelectric polarization. As a result, enhanced multiferroic properties of Bi0.8Ba0.2Fe0.975Nb0.025O3 ceramics with remanent magnetization and polarization (Mr and Pr) of 3.69 emu/g and 1.34 μC/cm2, respectively, were obtained. The reduction of low-frequency dispersion in permittivity and loss due to Nb substitution in Bi0.8Ba0.2FeO3 was observed in its dielectric response curve. An anomaly in the dielectric constant was observed in the vicinity of the antiferromagnetic transition temperature. Nb Substitution was found to be helpful to reduce loss, especially at lower frequencies. In addition, an enhancement in remanent polarization after poling the samples with x=0.015 and 0.025 in the dc magnetic field was evidence of magnetoelectric coupling at room temperature.