Enhanced energy storage in tungsten bronze-based ferroelectrics and MLCCs via a multi-coating engineering

High-power pulsed systems demand dielectric capacitors with high energy density and efficiency. Although perovskite ceramics dominate this field, simultaneously achieving high performance and fatigue endurance remains a significant challenge. Our study addresses this aim by incorporating a Ba_1-xSr_xTiO₃ second phase into tungsten bronze-type Ba_1-xSr_xNb_2-yTa_yO₆ matrix, followed by chemical coating with a SiO₂ layer. The prepared ceramics achieve an energy density of 21.1 J/cm³ with an efficiency of 84.5%. Furthermore, by combining a rational multilayer ceramic capacitor design with the thickness effect, an energy density of 23.2 ± 1.2 J/cm³ and an improved efficiency of 92.8 ± 0.4% are attained, representing a record energy density for tungsten bronze-based ceramics and capacitors. The dual-core-shell structure and compositional gradients induce lattice mismatch, boosting polarization and breakdown strength. The fabricated devices also demonstrate remarkable stability under varying frequency, temperature, and fatigue cycling conditions.