Enhanced Energy Density Driven by Dynamic Polar Nanoregions in BNT-Based Relaxor Ferroelectrics

Dielectric capacitors are attractive for sustainable energy storage owing to their ultrafast charge–discharge rates, high power density, and long lifetime. However, achieving high recoverable energy density under low electric fields remains challenging. In the present study, the above challenge of enhancing the energy density output at low electric fields in capacitive energy storage was addressed through the development of (1−x)Bi_0.35Na_0.35Sr_0.3TiO₃-xBaZr_0.15Ti_0.85O₃ [written as (1−x)BNST-xBZT; 0 ≤ x ≤ 0.15] materials employing a solid-state reaction process. The optimized 0.88BNST–0.12BZT composition exhibits a recoverable energy density of 4.49 J/cm³ and efficiency of 86.2 % at only 187 kV/cm, reflecting an exceptional low-field performance. The composition also shows excellent thermal (25–140 °C) and frequency (20–200 Hz) stability with negligible fatigue after 10⁵ cycles. These findings highlight the crucial role of PNR dynamics in achieving high energy density at low electric fields and offer a pathway for developing efficient, miniaturized ferroelectric capacitors.