Significantly enhanced energy-storage properties of Bi0.47Na0.47Ba0.06TiO3-CaHfO3 ceramics by introducing Sr0.7Bi0.2TiO3 for pulse capacitor application

The research and development of high-performance lead-free dielectric capacitors with excellent wide temperature stability, large recoverable energy density, ultra-high efficiency, and ultra-high-speed charging and discharging have received extensive attention. However, most lead-free dielectric materials developed at this stage do not meet all these requirements owing to various factors. Herein, a new type of lead-free (1-x)(0.94Bi0.47Na0.47Ba0.06TiO3-0.06CaHfO3)-xBi0.2Sr0.7TiO3 relaxor ferroelectric bulk ceramic was designed and prepared. The doping of Bi0.2Sr0.7TiO3 further refined the sub-micron grains and helped to obtain a wider band gap. Moreover, the ceramic exhibited a polarization response with almost no hysteresis, even under a high electric field because of the large number of randomly distributed nano-scale polar domains. The ceramic with x = 0.4 exhibited an outstanding comprehensive energy-storage performance with an extraordinary Wrec of 6.19 J/cm3 and a superior η of 93.5%. Similarly, another x = 0.45 ceramic also obtained a considerable energy-storage characteristic with an ultra-high η of 94.5% and a large Wrec of 6.02 J/cm3. In addition, the ceramic with x = 0.4 also showed remarkable wide frequency (1–200 Hz) and wide temperature range (20–140 °C) stability. In the pulse charge test, x = 0.4 ceramic exhibited a large discharge energy density of 5.07 J/cm3 under 340 kV/cm and a considerable discharge rate. All these indicate that our work provides a practical and effective idea for the design of application-type dielectric capacitors with an outstanding comprehensive performance.