Ultrahigh energy storage density in lead-free Bi0.5Na0.5TiO3-based relaxor ferroelectric ceramics under moderate electric fields via phase fraction manipulation

Abstract

Since electronic devices deteriorate when used in extremely high electric fields, it is essential to explore the potential of dielectric capacitors with high energy density under medium electric fields (MEFs). In this study, a polymorphic multiscale domain construction strategy was proposed to optimize the energy storage performance (ESP) of (1−x)Bi_0.5Na_0.5TiO₃-xCa(Ta_0.5Al_0.5)O₃ (xCTA, x = 0, 0.05, 0.1, 0.15, 0.2) under MEFs. The symbiosis of rhombic (R) + tetragonal (T) phase polar nanoregions (PNRs) was achieved through the design of Ca²⁺ and (Ta⁵⁺ + Al³⁺)⁴⁺ doping to phase ratios. This resulted in a significant recoverable energy density (W_rec) of 5.89 J cm⁻³ and an efficiency (η) of 87.4% at 370 kV cm⁻¹ for the 0.15CTA ceramic. In addition, the 0.15CTA ceramic exhibited excellent ESP stability (30 °C–200 °C and 1–200 Hz) and achieved ultra-high power density (P_d = 154 MW cm⁻³) and a fast discharge time (t_0.9 = 54.07 ns). This work presents a promising approach to boost the ESP of ceramic capacitors under MEFs.