Excellent energy storage performance with high breakdown strength in Nb2O5-modified (Bi0.5Na0.5)TiO3-based ceramics

Abstract

The development of lead-free dielectric capacitors with good energy storage performance and high reliability is of great practical significance for pulsed power systems. In this study, Nb2O5-modified 0.6(Bi0.5Na0.5)TiO3-0.4(Sr0.7Bi0.2)TiO3 (BNT-SBT-xNb, 0 ≤ x ≤ 0.07) ceramics were designed to enhance their energy storage performance and prepared using a hydrothermal method. The results show that Nb doping into the B site of BNT-SBT can induce lattice expansion and promote polar nanoregions, resulting in improved dielectric relaxation behavior. Moreover, the introduction of Nb can lead to the refinement of grain size, the increase in resistivity, the reduction of oxygen vacancies, and the broadening of band gap, thereby significantly enhancing the electrical breakdown strength (Eb). Accordingly, the BNT-SBT-0.05Nb system presents excellent energy storage performance with high Wrec ∼6.26 J/cm3 and η ∼87.9 % under an large Eb of 518 kV/cm in accompany with the wide temperature stability (Wrec and η vary within ±6.8 % and ±3.2 % at 40–100 °C). The significant improvement of Eb and energy storage performance demonstrates that the BNT-SBT-0.05Nb system is a potential candidate for applications in high-energy storage capacitors.