Multi-strategy optimization unlocks high energy density in lead-free NBT-CT ceramics

This work reports a multi-strategy approach to improve the energy storage performance (ESP) of 0.85Na_0.5Bi_0.5TiO₃-0.15CaTiO₃based lead-free ceramics. A small amount of (Li_0.5La_0.5)(Zr_0.8Ti_0.2)O₃(LLZT) was first introduced to reduce the sintering temperature and tailor the microstructure, resulting in the disruption of large ferroelectric domains and the formation of nanoscale polar regions. This modification led to increased breakdown strength and reduced remanent polarization (P_r), significantly improving energy storage performance. At an LLZT content of 15 %, the ceramic exhibited a recoverable energy density (W_rec) of 5.74 J·cm⁻³, along with an efficiency (η) of 85.5 % at 425 kV·cm⁻¹. Subsequent viscous polymer process (VPP) led to an increase in W_rec, reaching 10.08 J·cm⁻³at 845 kV·cm⁻¹, maintaining an efficiency of 85 %. The material also demonstrated excellent thermal and frequency stability, underscoring its promise for advanced dielectric energy storage applications. This study offers a new pathway for optimizing lead-free ceramics through combined compositional and processing strategies.