Bi_0.5Na_0.5TiO₃-Based Relaxor Ferroelectrics with Highly Polarizable Concentrated Nanodomains for High Capacitive Energy Storage under Moderate Electric Fields

The achievement of high recoverable energy density (<i>W</i>_rec) and efficiency (η) simultaneously in dielectric ceramics under low/moderate electric fields (<i>E</i>'s) offers potential for use in compact microelectronics and portable devices. However, a major challenge lies in the difficulty of coexistence of high maximum polarization (<i>P</i>_m) and low polarization hysteresis under low/moderate <i>E</i>'s. Here, through the modification of heterovalent ferroelectric-active ions to enhance average ionic polarizability, guarantee considerable spontaneous polarization, and disrupt long-range ferroelectric order, both the high <i>P</i>_m and low polarization hysteresis were obtained in the 0.80(Bi_0.47Na_0.47Ba_0.06)TiO₃-0.20Sr(Fe_0.5Nb_0.5)O₃ relaxor ferroelectric ceramics, leading to an excellent energy storage performance with <i>W</i>_rec of 6.17 J/cm³ and η of 90.3% under a moderate field of 34 kV/mm. In addition, the ceramics exhibit a high and temperature-stable permittivity (<i>ε</i>_r) as well as low dielectric loss, where <i>ε</i>_r (150 °C) reached 2085 with the temperature coefficient of capacitance (TCC) ≤ ±15% over 18 to 260 °C, and the tanδ at 150 °C is as low as 0.0075. This ceramic system exhibits potential in dielectric energy-storage capacitor systems for practical applications.