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

Abstract

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, Ag_1−2xCa_xNbO₃ 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 μC cm⁻², a large E_F of 179 kV cm⁻¹ and an E_b of 220 kV cm⁻¹ were achieved in Ag_0.92Ca_0.04NbO₃ 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 Ag_0.92Ca_0.04NbO₃ ceramics exhibited temperature-insensitive W_rec with minimal variation less than 1.5% from room temperature up to 100 °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 Ag_1−2xCa_xNbO₃ 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.