Superior energy storage density and efficiency in antiferroelectric-like BNT-based ceramics via single-element phase engineering

Bi_0.5Na_0.5TiO₃ (BNT) has received much attention because of its excellent dielectric properties for pulsed power systems. Most of the work has focused on inducing the relaxation behavior of BNT-based materials by doping with multiple elements, but the preparation method is complicated because a high maximum polarization (P_max) is sacrificed, which affects the energy storage properties. In this work, we induced antiferroelectric-like relaxor behavior by replacing Bi³⁺ with the single rare-earth ion Pr³⁺ to obtain highly active polar nanoregions (PNRs) that increase the energy storage efficiency (ƞ). In addition, the 6s² lone pair of electrons of Pr³⁺ can produce large ionic displacements similar to those of Bi³⁺. This could maintain the contribution of the A-site polarization to possess large P_max. Moreover, the high energy gap (E_g) and reliability increase the breakdown electric field (E_b). Consequently, the ultrahigh recoverable energy storage density (W_rec) of 11.01 J/cm³ at 552 kV/cm and η of 86.7% are achieved with (Bi_0.5−xPr_xNa_0.5)TiO₃ component (BPNT-18), which is superior to many other multielement components. It also has fast charging and discharging speeds (t_0.9 ≈ 37 ns) and high power densities (P_D ≈ 312 MW/cm³). This research proposes a simple and effective approach in which a single element is used to obtain excellent energy storage performance in lead-free dielectric ceramics.