Realizing ultrahigh energy storage performance in sodium bismuth titanate-based ceramics via local polarization engineering

Abstract

Dielectric capacitors, with high power density and a fast discharge rate, are one of the most promising environmentally friendly components for pulsed power systems. However, achieving high energy storage density (W_rec) while ensuring high energy storage efficiency (η) remains a great challenge. Herein, we designed a Bi_0.5Na_0.5TiO₃-based ceramic and achieved a high W_rec of 14.83 J cm⁻³ and a high η of 90.15% by regulating local polarization. This is achieved by adding Sm³⁺, Mg²⁺, and Ta⁵⁺, which have large differences in ionic radii and mismatched valence states. The mutual substitution of these ions results in polar clusters showing a disordered polarization state at the nanoscale. We confirmed by HAADF-STEM that the incorporated components effectively generate local random electric fields, resulting in local polarization fluctuations. This enables the ceramic to have a low remanent polarization (P_r). Furthermore, observing the microstructure of the ceramic through an electron microscope, nanoscale polar structures and small grain sizes are seen, contributing to an ultrahigh E_b strength of 810 kV cm⁻¹. This work provides a paradigm for the development of high-performance relaxor ferroelectric ceramics.