Enhanced Energy-Storage Properties of Ta Modified BNT - BT - NN Lead-Free Ceramics

Lead-free 0.9(0.92Bi(0.5)Na(0.5)TiO(3)-0.08BaTiO(3))-0.1(NaNb(1- (x) Ta-) (x) O-3) ceramics (abbreviated as BNBT - NN1- (x) T (x) ), x = 0, 0.25, 0.50, 0.75 and 1.00, were prepared by conventional solid-state mixed oxide route. The effects of Ta substitution on the crystal structure, morphology, dielectric, ferroelectric as well as energy-storage properties were systematically investigated. X-ray diffraction revealed a single-phase perovskite structure for x <= 0.75 with coexisting rhombohedral and tetragonal phases. With increasing Ta substitution, a weakening of tetragonal distortion was observed. The SEM micrographs of all samples displayed dense microstructure with an average grain size of 0.70-0.99 mu m. Good temperature stability of dielectric properties was maintained in the whole range of Ta substitution. The composition with x = 0.25 showed an optimum energy-storage density of 0.37 J/cm(3) and the energy-storage efficiency of 75.1% at 50 kV/cm, thus indicating the promising application of BNBT-NN1-xTx ceramics as energy-storage capacitors.