Entropy-driven multi-scale enhancement of energy storage performance in (Bi0.5Na0.5)0.5Ba0.5TiO3 ceramics

The dielectric ceramic capacitor serves as the core energy storage element in the pulsed power system. However, the inability to balance high energy storage density (W_rec) and energy storage efficiency (η) has become a technical challenge limiting the miniaturisation of pulsed power devices. This work proposes an entropy-driven strategy, through introducing Sr(Sc_0.5Nb_0.5)O₃ (SSN) as an end-member, to modulate the phase structure and suppress interfacial polarization in the medium entropy matrix, (Bi_0.5Na_0.5)_0.5Ba_0.5TiO₃ (BN50BT). The introduction of SSN endows BN50BT ceramics with a multiphase structure of P4mm and Pm-3m and successfully establishes a super-paraelectric (SPE) state at room temperature, improving the polarization response. Furthermore, the incorporation of SSN effectively suppresses interfacial polarization and enhances the E_b of the system. Thus, the 0.80[(Bi_0.5Na_0.5)_0.5Ba_0.5TiO₃]-0.20Sr(Sc_0.5Nb_0.5)O₃ ceramics exhibit a decent W_rec of 6.24 J/cm³ and a high η of 89.02%, along with remarkable stabilities over a wide frequency range (5–150 Hz) and temperature range (25–140 °C). This work demonstrates that the entropy-driven construction of a multiphase-coexisting SPE state, along with suppressed interfacial polarization, represents a feasible approach to optimizing the energy storage properties of dielectric ceramics.