The authors prepared Yb-doped bismuth iron oxide ceramics ͑Bi 1−x Yb x FeO 3 , with 0 ഛ x ഛ 0.20͒ by rapid liquid phase sintering method and investigated the material's structures and electrical properties. The x-ray diffraction measurements showed that the doping of Yb has induced noticeable lattice distortion in the ceramics, and a largest distortion was observed when the concentration of Yb was 15%. By doping electrical resistivity, ferroelectric and dielectric properties of the ceramics were improved. Among all samples, BiFeO 3 doped with 15% Yb was found to have the smallest leakage current density ͑Ͻ10 −7 A/cm 2 ͒ and the largest remnant polarization ͑8.5 C/cm 2 ͒. The compound BiFeO 3 ͑abbreviated as BFO͒ was first synthesized in the late 1950s. 1 Research in the early stage, which mainly focused on ceramics, revealed that BFO possesses a rhombohedrally distorted perovskite structure ͑lat-tice parameters a = b = c = 0.563 nm and ␣ = ␤ = ␥ = 59.4°͒ in addition to coupled ferroelectric ͑Curie temperature T C ϳ 1103 K͒ and antiferromagnetic ͑Neel temperature T N ϳ 643 K͒ behaviors at room temperature. Despite a high Curie temperature, the bulk BFO exhibits very weak ferroelectric behavior ͑e.g., the spontaneous polarization P s , is only ϳ3.5 C/cm 2 ͒. 2-5 BFO thin films have been studied since the late 1980s. 6 In 2003, Wang et al. reported that a very large ferroelectric polarization ͑remnant polarization P r ϳ 60 C/cm 2 ͒ has been achieved in a BFO thin film epitaxially grown on SrRuO 3 / SrTiO 3 . 7 The significantly enhanced polarization was interpreted as the result of a compressive stress imposed by the SrRuO 3 electrode, which has an in-plane lattice parameter smaller than that of BFO. Because of the compressive stress, the epitaxial BFO film has a tetragonal-like crystal structure ͑a = 0.394 nm, c = 0.400 nm, and ␣ = 89.5°͒ rather than the rhombohedral symmetry in bulk materials and therefore leads to large polarization. Since then more studies have reported with successful development of BFO thin films with polarizations ranging from 50 to 150 m/cm 2 . 2,8-10 Theoretical work has also been conducted to interpret the extraordinarily large ferroelectric polarization in BFO films. 11 The success in the thin film studies has in turn stimulated interest to produce bulk ceramics with improved properties. New processing techniques, such as rapid liquid phase sintering, have been developed to synthesize single-phase BFO ceramics. 12,13 The effect of compositional modification, either by forming of solid solution ͑e.g., with Pb͑Zr 1−x ,Ti x ͒O 3 ͒ 14 or by doping, has also been extensively studied. Quite a number of transition metal elements ͑e.g., Ni, Ti, Cr, and Mn͒ 15-18 and rare-earth elements ͑e.g., La and Nd͒ 19,20 have been employed as dopants. The authors are more interested in the doping of rare-earth elements because this may significantly change both the ferroelectric properties and magnetic behaviors of BFO which could possibly lead to enhanced magnetoelectric effect. 21,22 In this work, we repo...