Effects of (La, Sr) co-doping on electrical conduction and magnetic properties of BiFeO₃ nanoparticles

Multiferroic material as a photovoltaic material has gained considerable attention in recent years. Nanoparticles (NPs) La_0.1Bi_0.9-xSr_xFeO_y (LBSF, x=0, 0.2, 0.4) with dopant Sr²⁺ ions were synthesized by the sol-gel method. A systematic change in the crystal structure from rhombohedral to tetragonal upon increasing Sr doping was observed. There is an obvious change in the particle size from 180 nm to 50 nm with increasing Sr substitution into LBFO. It was found that Sr doping effectively narrows the band gap from ～2.08 eV to ～1.94 eV, while it leads to an apparent enhancement in the electrical conductivity of LBSF NPs, making a transition from insulator to semiconductor. This suggests an effective way to modulate the conductivity of BiFeO₃-based multiferroic materials with pure phase by co-doping with La and Sr at the A sites of BiFeO₃.