Investigation of Tb-doping on structural transition and multiferroic properties of BiFeO₃ thin films

Pure BiFeO₃ (BFO) and Bi_1-xTb_xFeO ₃ (BTFO) thin films were successfully prepared on FTO (fluorine doped tin oxide) substrates by the sol-gel spin-coating method. The effects of Tb-doping on the structural transition, leakage current, and dielectric and multiferroic properties of the BTFO thin films have been investigated systematically. XRD, Rietveld refinement and Raman spectroscopy results clearly reveal that a structural transition occurs from the rhombohedral (R3c:H) to the biphasic structure (R3c:H+R-3m:R) with Tb-doping. The leakage current density of BTFO_x=0.10 thin film is two orders lower than that of the pure BFO, i.e. 5.1×10^-7 A/cm² at 100 kV/cm. Furthermore, the electrical conduction mechanism of the BTFO thin films is dominated by space-charge-limited conduction. The two-phase coexistence of BTFO _x=0.10 gives rise to the superior ferroelectric (2P_r=135.1 μC/cm²) and the enhanced ferromagnetic properties (M _s=6.3 emu/cm³). The optimal performance of the BTFO thin films is mainly attributed to the biphasic structure and the distorted deformation of FeO₆ octahedra.