Currently, the development of dielectric ceramic capacitors is restricted by the contradiction between high efficiency and high recoverable density. Therefore, a novel strategy was designed to achieve a superior balance between them. Firstly, introducing Sr_0.85La_0.1TiO₃ can enhance the content of the weak polar phase (P4bm) to become the main component, which can optimize the relaxor behaviour and improve efficiency. Then, the electric breakdown strength was effectively enhanced by grain refinement and viscous polymer processing. Finally, a high recoverable energy density of ~5.3 J/cm³ and an excellent efficiency of ~92.2% were attained in 0.9Bi_0.5Na_0.5TiO₃-0.1Na_0.8Sr_0.1NbO₃ ceramic with the addition of 0.35Sr_0.85La_0.1TiO₃ after viscous polymer processing. The piezoelectric force microscope had been applied to prove the high activity of the polar nanoregions and finite element analysis was adopted to explain the reasons for the enhancing electric breakdown strength. In addition, this ceramic exhibits good temperature and frequency stability, and a fast discharging rate of 0.11 μs, making it a potential candidate for the actual application.

In the last few decades, dielectric capacitors have gotten a lot of attention because they can store more power and charge and discharge very quickly. But it has a low energy-storage density (W_rec), efficiency (η), and temperature stability. By adding Pb(Mg_1/3Nb_2/3)O₃ (PMN) and (Bi_0·1Sr_0.85)TiO₃ (BST) to a nonstoichiometric (Bi_0·51Na_0.5)TiO₃ (BNT) matrix, the goal is to change the phase transition properties and make the material more relaxor ferroelectric (RFE) by lowering the remnant polarization P_r and keeping the maximum polarization P_max. A viscous polymer process (VPP) is used to improve the electric breakdown strength, which is also a key part of being able to store energy. By working together, ceramics with the formula 0.79[0.85BNT-0.15PMN]-0.21BST (BP-0.21BST) are made. The phase structure has been changed from a rhombohedral phase to a rhombohedral-tetragonal coexisted phase. This is beneficial for RFE properties and gives a W_rec of 6.45 J/cm³ and a η of 90% at 400 kV/cm. Also, the energy-storage property is very temperature stable between 30 and 150 ℃. These results show that process optimization and composition design can be used to improve the energy storage properties, and that the dielectric ceramic materials made can be used in high-powder pulse dielectric capacitors.

Lead-free (Bi_0.5Na_0.5)TiO₃ (BNT)-based relaxor ferroelectric (RFE) ceramics have attracted a lot of attention due to their high power density and rapid charge-discharge capabilities, as well as their potential application in pulse power capacitors. However, because of the desire for smaller electronic devices, their energy storage performance (ESP) should be enhanced even further. We describe a defect engineering strategy for enhancing the antiferroelectric-like RFE feature of BNT-based ceramics by unequal substitution of rare-earth La³⁺ in this paper. The ESP of La³⁺-doped samples is raised by 25% with the same synthetic procedure and thickness, due to an increase in the critical electric field (E-field) and saturated E-field during polarization response, which is induced by a modification in the energy barrier between the lattice torsion. More impressively, an ultrahigh recoverable energy storage density W_rec of 8.58 J/cm³ and a high energy storage efficiency η of 94.5% are simultaneously attained in 3 at.% La³⁺-substituted 0.6(Bi_0.5Na_0.4K_0.1)LaTiO₃-0.4[2/3SrTiO₃-1/3Bi(Mg_2/3Ni_1/3)O₃] RFE ceramics with good temperature stability (W_rec = 4.6 ± 0.2 J/cm³ and higher η of ≥90% from 30 ℃ to 120 ℃), frequency stability, and fatigue resistance. The significant increase in ESP achieved through defect engineering not only proves the effectiveness of our strategy, but also presents a novel dielectric material with potential applications in pulse power capacitors.