High capacitive performances obtained in sandwich structured Bi_0.5Na_0.5TiO₃-based dielectric ceramics

As power electronics continue to advance and environmental concerns grow, high energy storage lead-free ceramic capacitors have become pivotal in dielectric materials research. However, the inherent compromise between improved dielectric polarization properties and increased breakdown strength persists as a primary constraint in advancing energy storage capabilities. To break through this shackle, sandwich structured Bi_0.5Na_0.5TiO₃-based lead-free ceramics are designed by alternatively arranging the relaxor ferroelectric layer with high polarization and the linear-like dielectric layer with high electric field breakdown and fabricated through tape casting and solid state sintering in this work. The material demonstrates exceptional energy storage capability featuring a record recoverable density of 11.02 J cm⁻³ and superior efficiency (79.1%) at 800 kV cm⁻¹. Remarkably, it maintains stable capacitive behavior across wide frequency (1–100 Hz) and temperature (30–160 °C) ranges, and fatigue cycles (1–10⁵). This breakthrough demonstrates that sandwich architecture synergistically resolves the polarization–breakdown strength paradox in lead-free ceramics, achieving simultaneous dielectric reinforcement and energy storage enhancement through interfacial engineering optimization.