Sr and Pb co-doping effect on the crystal structure, dielectric and magnetic properties of BiFeO3 multiferroic compounds

Bi1−x(Sr1/2Pb1/2)xFeO3 (0.10 ≤ x ≤ 0.30) multiferroic compounds have been synthesized by a conventional solid-state reaction. The influences of A-site Sr/Pb co-doping on the structure, dielectric and magnetic properties of BiFeO3 are investigated systematically. X-ray diffraction reveals that the crystal structure of Bi1−x(Sr1/2Pb1/2)xFeO3 transforms from the rhombohedral symmetry (space group R3c) to the cubic symmetry (space group Pm3¯ m) with Sr/Pb concentration increasing. Meanwhile, the intensities of BiO bond vibrations continuously decrease and finally disappear. The RT polarization versus electric field (P-E) curves confim the ferroelectric nature for all the samples. Furthermore, it is found that the dielectric constant and dielectric loss tangent of the samples measured in the frequency range of 100-107 Hz decrease drastically at room temperature. A considerable reduction in the leakage current is observed for BFO with Sr/Pb doping content increasing. The ferromagnetic property enhances with the Sr/Pb substitution increasing, which is ascribed to the cooperation of the Fe2+OFe3+ double exchange interaction and the effective suppression of antiferromagnetic cycloidal spin structure caused by the crystalline structure transformation. All results indicate that the Sr and Pb co-doping can effectively improve the magnetic and high-frequency dielectric properties of the multiferroic BiFeO3 compounds.