A novel lead-free relaxor ferroelectric ceramic of (0.67-x)BiFeO3-0.33BaTiO(3)-xBa(Mg1/3Nb2/3)O-3 [(0.67-x)BF-0.33BT-xBMN, x=0-0.1] was prepared by a solid-state reaction method. A relatively high maximum polarization P-max of 38 mu C/cm(2) and a low remanent polarization P-r of 5.7 mu C/cm(2) were attained under 12.5kV/mm in the x=0.06 sample, leading to an excellent energy-storage density of W similar to 1.56 J/cm(3) and a moderate energy-storage efficiency of eta similar to 75%. Moreover, a good temperature stability of the energy storage was obtained in the x=0.06 sample from 25 degrees C to 190 degrees C. The achievement of these characteristics was basically attributed to an electric field induced reversible ergodic to ferroelectric phase transition owing to similar free energies near a critical freezing temperature. The results indicate that the (0.67-x)BF-0.33BT-xBMN lead-free realxor ferroelectric ceramic could be a promising dielectric material for energy-storage capacitors.