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A strategy of mitigating polarization saturation is applied to enhance the energy storage properties of Sn-modified NBT–ST relaxor ceramics.

Dielectric capacitors with high energy storage performance are in great demand for emerging advanced energy storage applications. Relaxor ferroelectrics are one type dielectric materials possessing high energy storage density and energy efficiency simultaneously. In this study, 0.9(Sr0.7Bi0.2)TiO3–0.1Bi(Mg0.5Me0.5)O3 (Me = Ti, Zr, and Hf) dielectric relaxors are designed and the corresponding energy storage properties are investigated. The excellent recoverable energy density of 3.1 J/cm3 with a high energy efficiency of 93% is achieved at applied electric field of 360 kV/cm for 0.9(Sr0.7Bi0.2)TiO3–0.1Bi(Mg0.5Hf0.5)O3 (0.9SBT–0.1BMH) ceramic. High breakdown strength of 460 kV/cm in 0.9SBT–0.1BMH ceramic is obtained by Weibull distribution with satisfied reliability. In addition, 0.9SBT–0.1BMH shows outstanding thermal stability of energy storage performance up to 200°C, with the variation being less than 5%, together with satisfying cycling stability and high charge‐discharge rate, making the 0.9SBT–0.1BMH ceramic a potential lead‐free candidate for high power energy storage applications at elevated temperature.

Sodium niobate (NaNbO3)-based lead-free ceramics have been actively studied for energy storage applications because of their antiferroelectric and/or relaxor features achieved in modified systems. The P–E loops of NaNbO3-based ceramics are usually hysteretic because of the existence of a metastable ferroelectric phase at room temperature. In this study, by introducing aliovalent cations and A-site vacancies, the relaxor characteristics are greatly enhanced in (Na1–2x Bi x )­(Nb1–x Zr x )­O3 ceramics, leading to a high energy storage efficiency of above 90%. In addition, sintering aid CuO and a special ramp-to-spike sintering profile were employed to decrease the sintering temperature and reduce the grain size. The modified ceramic exhibits improved insulating properties and hence a higher breakdown strength, leading to a high recoverable energy density of 4.9 J/cm3 and a high energy efficiency of 88% at 430 kV/cm. The ceramic also exhibits satisfactory temperature stability over a wide temperature range from 25 to 125 °C and charge–discharge performance, making it a promising candidate for high-power dielectric energy storage applications.

Dielectric capacitors with high energy storage performance have been actively studied for emerging applications. In this work, a series of environmental friendly lead-free relaxor ferroelectric ceramics, (1 − x)(Ba 0.75 Sr 0.25 )TiO 3 −xBi(Mg 0.5 Hf 0.5 )O 3 with 0 ≤ x ≤ 0.5 [abbreviated as (1 − x)BST−xBMH], were synthesized by a high-temperature solid-state reaction method. The perovskite structure without any secondary phase can be obtained in samples with x ≤ 0.4. As the BMH content increases, the polarization−electric field (P−E) loop becomes slim and slanted. A large recoverable energy storage density of 4.3 J/cm 3 and high energy efficiency of 92% were achieved simultaneously in 0.6BST−0.4BMH at 390 kV/cm. The fine grain morphology with minimal porosity and the high conductivity activation energy were responsible for the enhanced breakdown strength. Of particular importance is that the 0.6BST−0.4BMH ceramic shows excellent temperature stability and cycling reliability with energy density variations below 3 and 4%, respectively. In addition, the 0.6BST−0.4BMH ceramic possesses fast discharge time (∼0.59 μs) with a high power density of 3.5 MW/cm 3 . All these merits reveal that the lead-free 0.6BST−0.4BMH relaxor ceramic is a promising candidate for high-temperature and high-power energy storage capacitor applications.