The effect of ion doping at different sites on the structure, defects and multiferroic properties of BiFeO3 ceramics

The polycrystalline samples of undoped BiFeO3, Ce doped BiFeO3 (Bi0.9Ce0.1FeO3) and Zr dpoped BiFeO3 (BiFe0.9Zr0.1O3) were prepared by rapid liquid phase sintering technique. The effects of A-site substitution with Ce and B-site substitution with Zr on the structure, defects and multiferroic properties of BiFeO3 ceramics were comparative investigated. Undoped and doped BiFeO3 samples are well crystallized in perovskite structure, whilst Ce and Zr doping results in slight distortion in the lattice structure. With Ce and Zr doping, the average grain sizes decrease. Positron annihilation lifetime measurements reveal that there are vacancy-type defects in the three samples, and Bi0.9Ce0.1FeO3 sample has the maximum open volume and concentration of the vacancy defect among those three samples. Both Ce and Zr doping can improve the leakage current, ferroelectric and magnetic properties, whereas Zr doping exhibited better ability. The better electric properties in BiFe0.9Zr0.1O3 may be due to the effective reduction of oxygen vacancies, Fe2+ and impurity phases by Zr doping. The cause for better magnetic properties in BiFe0.9Zr0.1O3 sample may be that the insertion of Fe vacancies and nonmagnetically active Zr4+ ions in antiferromagnetic Fe sublattice can effectively suppress the spiral spin modulation structure.