Design for high energy storage density and temperature-insensitive lead-free antiferroelectric ceramics

Dielectric capacitors with high power density and excellent temperature stability are highly demanded in pulsed power systems. AgNbO3-based lead-free antiferroelectric ceramics have been proven to be a promising candidate for energy storage applications. Nevertheless, the recoverable energy storage density (W-rec) still needs to be further improved to meet the requirements of the miniaturization and integration of pulsed power systems. In order to significantly increase W-rec, a strategy, by introducing A-site vacancies, stabilizing antiferroelectricity and decreasing the grain size, is proposed in this work. Here, Ag1-2xCaxNbO3 solid solutions were designed for achieving high maximum polarization (P-max), large antiferroelectric-ferroelectric electric field (E-F) and high breakdown electric field (E-b). A high P-max of 39.6 mu C cm(-2), a large E-F of 179 kV cm(-1) and an E-b of 220 kV cm(-1) were achieved in Ag0.92Ca0.04NbO3 ceramics, leading to an ultrahigh W-rec of 3.55 J cm(-3). The significantly improved W-rec is about 2 times as high as that of the pure AgNbO3 counterpart. Meanwhile, the Ag0.92Ca0.04NbO3 ceramics exhibited temperature-insensitive W-rec with minimal variation less than 1.5% from room temperature up to 100 degrees C. A Ginzburg-Landau-Devonshire (GLD) phenomenology was proposed to reveal the increased stability of antiferroelectricity and the temperature-insensitive W-rec, which suggested that they are closely associated with the tailoring of free energy barriers for antiferroelectric-ferroelectric phase transition. The excellent energy storage performance makes the Ag1-2xCaxNbO3 system a good candidate for advanced pulsed power capacitors. More importantly, our findings open a new way for developing high performance AgNbO3-based and other lead-free systems for energy storage.