Valence modulation induced high-energy storage properties in BNT-based ceramics

High-performance lead-free dielectric ceramics are key to energy storage ceramic capacitors. In this work, an effective strategy was adopted to improve the dielectric energy storage properties (ESP) of Bi0.5Na0.5TiO3 based ceramics using CeO2 doping. The introduction of Ce4+ refines the grain size and improves the dielectric temperature stability of the (1-x)Bi0.4Na0.4Ca0.2TiO3-xCeO2 ceramics. However, Ce4+ is susceptible to reductive valence changes at high temperatures, forming defects that deteriorate the breakdown electric field strength (Eb). To address this issue, Ce4+ valence transitions were successfully inhibited by sintering ceramics in an oxygen atmosphere. Remarkably, the Eb value increases from 160 kV cm−1 for x = 0 wt% to 220 kV cm−1 for x = 0.8 wt%, and the total energy storage density increases from 1.38 J cm−3 to 2.99 J cm−3, as well as realizing a high energy storage efficiency (η ∼ 81 %). This study offers a framework for optimizing the performance of BNT-based energy storage ceramics and elucidating the precise link between valence variations and ESP.