Aliovalent A-site engineered AgNbO3 lead-free antiferroelectric ceramics toward superior energy storage density
Lead-free dielectric capacitors with high energy storage density and temperature-insensitive performance are pivotal to pulsed power systems. In this work, a pronounced recoverable energy storage density (Wrec) was achieved in AgNbO3-based lead-free antiferroelectric ceramics, by aliovalent A-site Sm mediation. The Sm modification was found to alter the crystal structure and enhance the interaction among the ions by affecting the electronic structure, leading to improved antiferroelectricity. The Sm0.03Ag0.91NbO3 solid solution exhibited a superior Wrec of 5.2 J cm−3 with a high energy storage efficiency (η) of 68.5% at an applied electric field of 290 kV cm−1. Excellent temperature stability of Wrec with a minimal variation of less than 4% from room temperature up to 140 °C was also observed. Meanwhile, the Sm0.03Ag0.91NbO3 ceramic also exhibited an ultrafast discharge speed (∼20 μs) and high discharge energy density (4.2 J cm−3). Ginzburg–Landau–Devonshire (GLD) phenomenology revealed that the significantly stabilized antiferroelectricity and the cation disorder were responsible for the ultrahigh Wrec and η. The extraordinary energy storage performance indicates the SmxAg1−3xNbO3 system a promising candidate for advanced pulsed power capacitors. More importantly, the results show that aliovalent A-site engineering is an effective way to achieve high energy storage density.