Realizing outstanding energy storage performance in BNST-based lead-free ceramics via introducing pyrochlore phase La2Zr2O7

Abstract

Lead-free dielectric ceramic materials with high recoverable energy storage density and efficiency have attracted significant attention for the development of next-generation pulse power capacitors. Among these, Bi_0.39Na_0.36Sr_0.25TiO₃ (BNST)-based ceramics exhibit excellent dielectric properties, but their applications are constrained by large remnant polarization and low dielectric breakdown field strength. To address this, pyrochlore-structured La₂Zr₂O₇ (LZO) is introduced into the BNST matrix to improve the energy storage performance. The introduction of LZO effectively inhibits long-range ferroelectric ordering in BNST while inducing the formation of dynamic polar nano-regions (PNRs). The grain refinement and microstructural densification increase the activation energy, leading to an increase in E_b. The BNST-0.09LZO ceramic shows the expected W_rec (∼6.2 J cm⁻³) and η (∼84.5%) at 375 kV cm⁻¹, together with outstanding temperature stability (the variation in P_max is within 6.2% in the temperature range of 40–200 °C) and frequency stability (the variation in P_max is within 2.85% in the frequency range of 1–150 Hz). Besides, the ceramics demonstrate a high power density of 79.58 MW cm⁻³ at 200 kV cm⁻¹ with a fast discharge performance of t_0.9 ∼38.3 ns. This work provides a novel method to enhance the performance of BNST-based materials for potential applications in the field of advanced pulse capacitors.