The magnetoelectric coupling in rhombohedral-tetragonal phases coexisted Bi _0.84Ba _0.20FeO ₃

Ba doped Bi _1.04-xBa _xFeO ₃ ceramics with x up to 0.30 have been prepared by the tartaric acid modified sol-gel method. The X ray diffraction patterns show that the structure transforms from rhombohedral to tetragonal with increasing the Ba substitution concentration from 10% to 30% and the coexistence of distorted rhombohedral and tetragonal phases in 20% Ba substituted BiFeO ₃, which was further confirmed by the Raman spectra. Bi _0.84Ba _0.20FeO ₃ exhibits the highest magnetization (1.6 emu/g under magnetic field of 12 kOe) compared with the other samples of different Ba substitution concentration. Significant enhancement of the ferroelectricity has been observed in 20% and 30% Ba substituted BiFeO ₃ with saturate polarization close to 6.6 μC/cm ² for Bi _0.74Ba _0.30FeO ₃. The magnetoelectric coupling of Bi _0.84Ba _0.20FeO ₃ has been measured and the maximum decrease of magnetization under magnetic field of 9.8 kOe was about 0.06 emu/g with increasing applied electric field to 11 kV/cm, and the magnetoelectric coefficient is 1.5×10 ^-12 s/m.