Structural Evolution-Enabled BiFeO3 modulated by strontium doping with enhanced magnetic and photoelectric performance

Ion doping is one of promising methods for enhancing the versatility of bismuth ferrite, BiFeO3. In this work, a structural phase transition of Bi1-xSrxFeO3 (0 < x < 1) nanoparticles (NPs) from rhombohedral to cubic occurs when the doping amount of strontium (Sr) reaches x = 0.25, which leads to a magnetic transformation from antiferromagnetic to ferromagnetic in Bi0.75Sr0.25FeO3 and Bi0.65Sr0.35FeO3. Comparing all the Sr-doped samples, the saturation magnetization and the residual magnetization of Bi0.75Sr0.25FeO3 are increased by approximately one order of magnitude, reaching the maximum of 1.859 emu/g and 0.046 emu/g, respectively. Meanwhile, an unanticipated 3 to 4-times higher photo-conductivity is found in Bi0.75Sr0.25FeO3, which is attributed to the bandgap reduction induced by phase transition and the increase in density of unoccupied oxygen vacancies. This work is beneficial for the study of the tuneable ferromagnetic properties of BiFeO3 at room temperature and opens up one new way to improve the electrical and electrochemical properties.