Dielectric capacitors with high power density and fast charge-discharge speed play an essential role in the development of pulsed power systems. The increased demands for miniaturization and practicality of pulsed power equipment also necessitate the development of dielectric materials that possess high energy density while maintaining ultrahigh efficiency (η). In particular, ultrahigh efficiency signifies minimal energy loss, which is essential for practical applications but challenging to effectively mitigate. Here, we demonstrate a strategy of incorporating heterovalent elements into Ba(Zr_0·1Ti_0.9)O₃, which contributes to achieving relaxor ferroelectric ceramics and reducing lattice strain, thereby improving the comprehensive energy storage performance. Finally, optimal energy storage performance is attained in 0.85Ba(Zr_0·1Ti_0.9)O₃-0.15Bi(Zn_2/3Ta_1/3)O₃ (BZT-0.15BiZnTa), with an ultrahigh η of 97.37% at 440 kV/cm (an advanced level in the lead-free ceramics) and an excellent recoverable energy storage density (W_rec) of 3.74 J/cm³. Notably, the BZT-0.15BiZnTa ceramics also exhibit exceptional temperature stability, maintaining fluctuations in W_rec within ~10% and η consistently exceeding 90% across the wide temperature range of −55 ℃ to 160 ℃, and under a high electric field of 250 kV/cm. All these features demonstrate that the relaxor and lattice strain engineering strategies have been successful in achieving high-performance lead-free ceramics, paving the way for designing high-efficiency dielectric capacitors with a wide temperature range.

Electrostatic energy storage technology based on dielectrics is the basis of advanced electronics and high-power electrical systems. High polarization (P) and high electric breakdown strength (E_b) are the key parameters for dielectric materials to achieve superior energy storage performance. In this work, a composite strategy based on antiferroelectric dielectrics (AFEs) has been proposed to improve the energy storage performance. Here, AlN is selected as the second phase for the (Pb_0.915Ba_0.04La_0.03)(Zr_0.65Sn_0.3Ti_0.05)O₃ (PBLZST) AFEs, which is embedded in the grain boundaries to construct insulating networks and regulate the local electric field, improving the E_b. Meanwhile, it is emphasized that AFEs have the AFE–FE and FE–AFE phase transitions, and the increase of the phase transition electric fields can further improve the recoverable energy density (W_rec). As a result, the E_b increases from 180 to 290 kV·cm⁻¹ with a simultaneous increase of the phase transition electric fields, magnifying the W_rec to ~144% of the pristine PBLZST. The mechanism for enhanced E_b and the phase transition electric fields is revealed by the finite element simulation method. Moreover, the PBLZST:1.0 wt% AlN composite ceramics exhibit favorable temperature stability, frequency stability, and charge–discharge ability, making the composite ceramics a promising candidate for energy storage applications.

Electrocaloric effect, i.e., the entropy and temperature changes arising from phase transition and dipole orientation induced in electric fields, can realize heat transport and refrigeration. The electrocaloric cooling eliminates the use of environmentally harmful coolants, possesses high cooling efficiency, small size and low weight as a promising environmental-friendly and high-efficiency cooling. One key point for electrocaloric cooling toward practical cooling is to enhance the performance of the electrocaloric effect of ferroelectrics. Ferroelectric ceramics have attracted much attention due to their high polarization, rich phase structures and variety of regulation methods. In this review, we introduced the electrocaloric effect of ferroelectric ceramic thin films, bulks and multilayer thick films with various compositions, and discussed the internal relations among electrocaloric effect, compositions, phase transition behaviors and microstructures. Furthermore, we concluded the modulation approaches of the electrocaloric effect of ferroelectric ceramics, and gave the future development of electrocaloric materials.