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 (W-rec), a high energy storage efficiency (eta) 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 W-rec of lead-free dielectric ceramics is usually achieved at the cost of eta, 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 W-rec, a high eta and excellent thermal stability. Herein, we propose a new strategy to tailor the temperature region between the temperature corresponding to the maximum dielectric permittivity (T-m) and the Burns temperature (T-B) of relaxor ferroelectrics to room temperature via composition optimization, to explore lead-free bulk ceramics with high comprehensive energy storage properties. A large W-rec of 3.51 J cm(-3) and a high eta of 80.1% are simultaneously obtained in 0.86NaNbO(3)-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 eta of 0.86NN-0.14BNH ceramics show good temperature stability over 20 degrees C to 200 degrees 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.