Significantly enhanced energy storage performance of rare-earth-modified silver niobate lead-free antiferroelectric ceramics via local chemical pressure tailoring

Abstract

Silver niobate (AgNbO₃) is considered as one of the most promising lead-free replacements for lead-containing antiferroelectric (AFE) ceramics, and has been drawing progressively more attention because of its relatively high energy storage density. However, weak ferroelectricity in pure AgNbO₃ exerts a negative impact on the energy storage performance, thus impeding the application of AgNbO₃-based ceramics in high-power systems. In this study, an A-site doping strategy was employed to suppress the ferroelectric distortion and boost the AFE distortion of AgNbO₃, based on local chemical pressure tailoring. An ultrahigh recoverable energy density (W_rec) of 4.5 J cm⁻³ was achieved in Ag_0.88Gd_0.04NbO₃ ceramics, which is superior to that of other reported lead-free systems. The enhancement of energy storage performance is ascribed to two reasons: first, antiferroelectricity could be boosted by smaller ions and suitable vacancies on A-sites, evidenced by X-ray diffraction patterns, Raman spectroscopy, and selected-area electron diffraction measurements. Moreover, the decreasing freezing temperature (T_f) and the increasing forward switching field (E_F) as well as backward switching field (E_A) with the increment of the gadolinium (Gd) content also confirmed the enhanced antiferroelectricity in Gd-doped AgNbO₃ ceramics. Second, the introduction of Gd₂O₃ could effectively decrease the grain size and increase the dielectric breakdown strength (DBS = 290 kV cm⁻¹). The performance due to local chemical pressure tailoring makes Gd-doped AgNbO₃ materials the most promising energy storage lead-free ceramics for dielectric energy storage capacitors.