Realizing high comprehensive energy storage performance in lead-free bulk ceramics via designing an unmatched temperature range†
The study of lead-free dielectric ceramics for capacitors has become one of the most active academic research areas in advanced functional materials owing to the environmental regulations. A large recoverable energy storage density (Wrec), a high energy storage efficiency (η) and good temperature stability in lead-free dielectric ceramics are highly desired simultaneously to meet the requirements of light weight and integration of dielectric capacitors in pulsed power devices. Unfortunately, a large Wrec of lead-free dielectric ceramics is usually achieved at the cost of η, and vice versa, hindering their practical applications. More importantly, despite the considerable efforts made so far to develop a large amount of lead-free bulk ceramics for dielectric capacitor applications, there is still a lack of scientific and feasible guidelines on how to design new material systems with a large Wrec, a high η and excellent thermal stability. Herein, we propose a new strategy to tailor the temperature region between the temperature corresponding to the maximum dielectric permittivity (Tm) and the Burns temperature (TB) of relaxor ferroelectrics to room temperature via composition optimization, to explore lead-free bulk ceramics with high comprehensive energy storage properties. A large Wrec of 3.51 J cm−3 and a high η of 80.1% are simultaneously obtained in 0.86NaNbO3–0.14(Bi0.5Na0.5)HfO3 (0.86NN–0.14BNH) ceramics under an electric field of 350 kV cm−1, leading to an excellent comprehensive energy storage performance in lead-free bulk ceramics. Furthermore, both the Wrec and η of 0.86NN–0.14BNH ceramics show good temperature stability over 20 °C to 200 °C at 280 kV cm−1, which is superior to that of other lead-free bulk ceramics. Most importantly, this work provides significant guidelines for designing new high-performance bulk ceramics for electrical energy storage applications.