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

Lead-free 0.9(0.92Bi0.5Na0.5TiO3–0.08BaTiO3)–0.1(NaNb(1-x)TaxO3) ceramics (abbreviated as BNBT − NN1-xTx), 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 µm. 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/cm3 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.