Modulation of oxygen vacancies optimized energy storage density in BNT-based ceramics via a defect engineering strategy

Abstract

Lead-free (Bi_0.5Na_0.5)TiO₃ (BNT)-based relaxor ferroelectric (RFE) ceramics have demonstrated great potential for application in pulsed power capacitors due to their high power density. However, with the urgent requirement for miniaturisation of electronic devices, the energy storage performance (ESP) of Na_0.5Bi_0.5TiO₃ (BNT)-based ceramics still needs to be further improved. This paper describes a defect engineering strategy to reduce oxygen vacancies in BNT-based RFE ceramics by equivalent substitution of high-valence Ta⁵⁺. Consequently, the breakdown strength of the Ta⁵⁺-doped samples is significantly improved, which is primarily attributed to the reduction in dielectric loss resulting from the diminution of the oxygen vacancy content. In particular, for the Bi_0.3Na_0.3Sr_0.28Sm_0.08Ti_0.98Ta_0.02O₃ ceramics, both an ultra-high energy storage density of ∼6.77 J cm⁻³ and a high energy storage efficiency of ∼87.5% are obtained. In addition, the Bi_0.3Na_0.3Sr_0.28Sm_0.08Ti_0.98Ta_0.02O₃ ceramics exhibit favourable electrical stability and fast charge/discharge rates (∼65 ns), which indicates tremendous potential for practical application in pulse capacitors. The significant improvement in ESP achieved via a defect engineering strategy provides a new approach for modification of dielectric capacitors.