Improved energy storage performance in rare-earth modified lead-free BNT-based relaxor ferroelectric ceramics

Dielectric ceramic capacitors with high energy storage performance are indispensable components in high-power pulse electronic systems. Herein, a collaborative optimization design is employed to achieve excellent energy storage performance in rare-earth oxides modified 0.76(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-0.24Sr0.7Bi0.2TiO3 (BNBT-SBT) ceramics by simultaneously enhancing the breakdown field strength (Eb) and relaxor behavior. To this end, ferroelectric domains are partially transformed into polar nanoregions by introducing relaxor ferroelectric SBT, while a smaller grain size is produced by doping rare-earth elements to improve the Eb and further disrupt the long-range order of ferroelectric polarization. It is found that the La-doped BNBT-SBT ceramic simultaneously exhibits a superior energy storage density of 4.4 J cm−3 and an ultrahigh efficiency of ∼91% under a moderate electric field of 300 kV/cm. The good temperature stability (30–120 °C), frequency endurance (1–100 Hz), electric fatigue resistance (1–106 cycles), and excellent power density (108 MW cm−3) are also obtained in the lead-free Bi0.5Na0.5TiO3-based relaxor ferroelectric ceramics. These prominent properties indicate that the La-doped BNBT-SBT ceramic is a promising candidate for applications of high-energy storage capacitors.