Excellent energy-storage performance realized in SANNS-based tungsten bronze ceramics via synergistic optimization strategy

A series of tungsten bronze (Sr2–xBixAg0.2Na0.8)(Nb4.8–xZrxSb0.2)O15 compounds were fabricated by solid-state method to systematically study the impacts of co-doping Bi3+/Zr4+ ions in A/B-sites on the structures, relaxor characteristics, and energy-storage performances. The relationship between structures and relaxor behaviors are summarized as three main points: (1) with increasing the amount of co-doping Bi3+/Zr4+ ions, the crystal structure evolved from an orthorhombic Bbm2 to a tetragonal paraelectric P4/mbm symmetry at room temperature; (2) enhancing relaxor characteristics at room temperature was achieved by tailoring the temperature region of Tm−TB (Tm is the dielectric maximum temperature, TB is the Burns temperature), which could be attributed to the incommensurate local structure modulations associated with the orthogonal distortion of P4bm symmetry and the appearance of microdomains; (3) The co-introduction of Bi3+ and Zr4+ could also played an important role in inhibiting the grain sizes, increasing resistivity and band-gap to enhance the breakdown strength. Finally, a superior recoverable energy-storage density (3.61 J/cm3) and an ultrahigh energy efficiency (90%) were obtained simultaneously at 389 kV/cm in BZ0.05 ceramics. Moreover, an outstanding power density (158.98 MW/cm3) together with a current density of 1422.29 A/cm2 was realized at 220 kV/cm from the charging−discharging performance measurements. The excellent energy-storage performance (ESPs) make the environmentally friendly BZ0.05 samples show enormous potential in high-power capacitor applications.