Superior energy storage and stability in antiferroelectric-doped relaxor ferroelectric ceramics

With the rapid advancement of electrification, power devices are trending toward greater miniaturization, placing increasing demands on dielectric materials. A central challenge in advancing next-generation pulsed power and capacitor technologies, particularly in lead-free systems, lies in achieving high energy storage performance (ESP), characterized by a large recoverable energy density (W_rec), high efficiency (η), and robust stability under varying electric fields (E-fields). We report a rationally designed series of antiferroelectric-phase-doped relaxor ferroelectric ceramics with the composition (1–x)[Bi_0.51(Na_0.82K_0.18)_0.5]TiO₃-xNaNbO₃(x = 0.22–0.28), synthesized via a conventional solid-state route. The design strategy centers on disrupting long-range ferroelectric order to promote the formation of polar nanoregions, while simultaneously stabilizing a multiphase coexistence of rhombohedral (R3c) and orthorhombic (Pbcm) symmetries. This structural interplay gives rise to pronounced relaxor ferroelectric behavior. The materials were subsequently processed using a viscous polymer processing technique to enhance dielectric breakdown strength. This compositional optimization enabled the x = 0.28 sample to achieve an ultrahigh ESP, delivering a W_recof 7.91J/cm³and an η of 80 % under an E-field of 490 kV/cm. The ceramics also demonstrated remarkable stability across a broad frequency range (1–200 Hz) and temperature window (30–150 °C). This work demonstrates the feasibility of enhancing energy storage performance, while providing a scalable route toward thermally and frequency-stable lead-free capacitors and laying the groundwork for future practical deployment.