Energy storage behavior optimization of SBKT ceramics based on multi-sites charged defects synergistic regulation engineering

Abstract Lead-free relaxor ferroelectric ceramic is suitable for pulse energy storage. Achieving both high energy storage density and efficiency is crucial for the research. Herein, (1-x)(0.5Sr0.7Bi0.2TiO3-0.5K0.5Bi0.5TiO3)-xNaTaO3 relaxor ferroelectric ceramic is fabricated to optimize microstructures and energy storage behavior based on multi-sites charged defects synergistic regulation engineering. Na+ doping in A-site contributes to polymorphic polarization; Ta5+ doping in B-site refines grain and increases the electrical resistance; the formation and migration process of oxygen vacancy charged defects are significantly suppressed in O-site based on ion doping and the formation of Bi2Ti2O7-based insulating phase. The introduction and synergistic regulation of these charged defects enhance the ionic and charge disorder and configurational entropy, and induces more small-sized polar structure, resulting in the enhanced relaxor ferroelectricity and delayed polarization saturation. Meanwhile, the micromorphology is improved, resulting in the enhanced electrical insulation. Consequently, the polarization and breakdown behavior are optimized. 0.9(0.5Sr0.7Bi0.2TiO3-0.5K0.5Bi0.5TiO3)-0.1NaTaO3 exhibits low remnant polarization, high breakdown strength and maximum polarization, and achieves high energy storage density of 5.68 J/cm3 with high efficiency of 88.1% at moderate operating electric fields 490 kV/cm, and excellent temperature (-50~150 °C), frequency (10~500 Hz), and cycling stability. Meanwhile, the sample shows good pulsed charging-discharging properties with thermal stability and long cycle life (105 cycles at 25 °C and 150 °C). Therefore, this sample demonstrates promising potential for pulse energy storage, and this study offers a novel strategy and mechanism for the designing and optimization of advanced energy storage ceramics.