Significantly enhanced energy storage performance of rare-earth-modified silver niobate lead-free antiferroelectric ceramics via local chemical pressure tailoring
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 (Wrec) of 4.5 J cm−3 was achieved in Ag0.88Gd0.04NbO3 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 (Tf) and the increasing forward switching field (EF) as well as backward switching field (EA) 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.