Defect dipole engineered hybrid polar configurations for high dielectric energy storage under low electric fields

Abstract

Dielectric capacitors are vital components in advanced electronics and high-power electrical systems. A persistent challenge, however, is enhancing their energy density (Wrec) at low electric fields and voltages. Herein, we design a defect dipole engineered hybrid polar configuration to address this issue. By introducing defect dipoles in Na0.5Bi0.5Ti1–xAlxO3 (NBTA-x) films, tailored polar configurations comprising a ferroelectric domain matrix and sparse polar nanoregions are precisely engineered. The coexistence of macro- and micro-domains in the optimal proportion improves interdomain interactions, effectively suppressing hysteresis while still retaining ferroelectric polarization. Meanwhile, the depolarization field generated by defect dipoles drives the aligned domains to revert to their initial disordered state. Together, this dual mechanism weakens remanent polarization (Pr), enabling the simultaneous reduction of energy loss (Wloss) and enhancement of Wrec. Under a low electric field of 1756 kV cm−1, the NBTA-0.2 relaxor ferroelectric film delivers a high Wrec of 66.2 J cm−3 with an efficiency exceeding 70%. This work offers a generalizable strategy for developing high-performance dielectrics operating at low fields and voltages, benefiting from microscopic domain architecture and defect dipole design.