Sr_0.775Bi_0.15TiO₃ ceramics with linear-like relaxor ferroelectric behavior are promising dielectric energy storage materials. Improving breakdown strength (BDS) is key to optimizing its energy storage performance and expanding its application. Herein, a multi-scale synergistic optimization strategy is employed by introducing Cd²⁺ in Sr_0.775Bi_0.15TiO₃ ceramics to improve the BDS and energy storage performance, and the underlying mechanism of performance optimization is systematically investigated. At the nanoscale, first-principles calculations combined with electrical testing and structural characterization reveal that Cd²⁺ doping increases the ionic disorder, A–O bond strength, and the formation energy and migration barrier of oxygen vacancies. This inhibits oxygen vacancy transport and enhances electrical insulation. At the microscale, numerical simulations verify that the composition with appropriate doping exhibits a small and uniform local electric field. This decreases the breakdown probability. Meanwhile, Cd²⁺ doping enhances relaxor ferroelectricity. Consequently, the BDS is improved while maintaining low remnant polarization, and the optimized Cd_0.05Sr_0.725Bi_0.15TiO₃ ceramic exhibits excellent comprehensive energy storage performance with a high recoverable energy density of 5.16 J/cm³ and an efficiency of 92.65 % under 490 kV/cm. The performance possesses outstanding stability over a broad temperature range (21–150 °C), a wide frequency range (10–1000 Hz), and up to 10⁵ charge–discharge cycles. This sample also shows a high-power density of 115.02 MW/cm³ and an ultrafast discharge time of 0.046 μs. Therefore, Cd_0.05Sr_0.775Bi_0.15TiO₃ ceramic is promising for advanced pulsed-power capacitor applications, and this work provides additional mechanisms and strategic guidance for improving BDS and energy storage performance of linear-like relaxor ferroelectrics.

The exploration of high-performance dielectric ceramics with dielectric constants lower than 10 is of great significance for the next generation of wireless communication. In this study, we reported the Yb₂Si₂O₇ (YSO) dielectric ceramics synthesized using a facile solid-state reaction technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization confirmed that YSO ceramics had a monoclinic structure. At a sintering temperature of 1500 °C, the sintered sample reached a maximum relative density of 96% and demonstrated the best dielectric properties: dielectric constant (ε_r) = 7.57, Q×f = 78,645 GHz (Q is quality factor, and f is the resonant frequency of 13.5 GHz), andtemperature coefficient of the resonant frequency (τ_f) = −13.5 ppm/°C. Moreover, Raman analysis revealed that the Si–O bond dominated the lattice vibration, and the full width at half maximum (FWHM) of the strong peak at 922 cm⁻¹ was inversely proportional to the Q×f value. According to the Phillips–van Vechten–Levine (P–V–L) theory, the values of Q×f and τ_f are affected primarily by the Si–O bond, while ε_r is influenced mainly by the Yb–O bond. YSO ceramics demonstrated excellent dielectric properties in the terahertz band (ε_r = 8.13, Q×f = 112,758 GHz), making them promising candidates for future applications in the terahertz band.

Sr_0.7Bi_0.2TiO₃ (SBT) by increasing the proportion and size of polar nano-region. Meanwhile, the BDS remains a high level with x ≤ 0.38 attributed to the addition of KBT with a large band gap. As a result, the 0.62SBT-0.38KBT exhibits a high energy storage density of 2.21 J/cm³ with high η of 91.4% at 220 kV/cm and superior temperature stability (−55 ~ 150 °C), frequency stability (10 ~ 500 Hz) and fatigue resistance (10⁵ cycles). Moreover, high pulsed discharge energy density (1.81 J/cm³), high power density (49.5 MW/cm³) and great thermal stability (20 ~ 160 °C) are achieved in 0.62SBT-0.38KBT. Based on these excellent properties, the 0.62SBT-0.38KBT are suitable for pulsed power systems. This work provides a novel strategy and systematic study for improving energy storage properties of SBT.