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Ceramic capacitors require promising energy storage properties to meet the demands of electronic industry which can be tailored by ferroelectric polarization and electrical breakdown strength. Electrical breakdown exhibits close relation to leakage current in advanced dielectric materials when stimulated by high levels of electric field. The suppression of leakage can be an effective strategy to elevate dielectric breakdown. In this work, Zr ions were employed to replace Ti ions in Ba0.3Sr0.7TiO3 ceramics to achieve the improvement of dielectric breakdown and then increase energy storage ability. Zr doping can obviously reduce the leakage current more than an order of magnitude by blocking the path between two adjacent Ti ions and increasing the distance of electron hopping. A promising energy storage density can be obtained with good fatigue endurance upto cycles of 105. This indicates that the strategy of suppressing leakage by trace amount of Zr doping is an effective approach to tailor energy storage behavior of dielectric ceramics.

The ability of storing electrostatic energy for a capacitor is largely dependent on the energy storage performances of the material used in the electronic components. In this case, a composition-driven Bi0.5Na0.5TiO3-based system, (1−x)(0.84Bi0.5Na0.5TiO3−0.16Bi0.5K0.5TiO3)−xBi(Mg0.5Ti0.5)O3 (NTB-KBT-100xBMT, x = 0.04–0.14) was designed and the enhanced energy storage density and efficiency with good thermal insensitivity were confirmed. The introduction of BMT can induce the relaxor characteristic due to the deconstruction of the ferroelectric long-range order, leading to the increase in dielectric breakdown and the improved energy storage performances. Particularly, the NTB-KBT-8BMT ceramic exhibits a high stored energy density (Wtotal = 2.88 J/cm3) and recoverable energy density (Wrec = 2.42 J/cm3) with good energy efficiency (η = 84.0%) under 320 kV/cm, indicative of potential application for energy storage components. Moreover, the NTB-KBT-8BMT ceramic exhibits typical temperature-independent character in a wide temperature range from 30 to 140 °C due to broad diffused phase transition. It can be concluded that constructing relaxor ferroelectrics is an effective approach to design novel dielectrics for pulse power applications.