Modulated band structure and phase transitions in calcium hafnate titanate modified silver niobate ceramics for energy storage

Abstract Lead-free silver niobate (AgNbO3, AN)-based dielectric ceramics have attracted intense attention for high-power energy storage applications since 2016 due to their electric-field-assisted antiferroelectric-ferroelectric phase transition. In this work, chemical compositions of 0.2 wt.% Mn-doped (1-x)AgNbO3-xCa(Hf0.2Ti0.8)O3 (AN-CHTx, x = 0.00–0.08) were designed and their ceramic samples were prepared in flowing oxygen via solid-state route. Our results show that the CHT modification not only enhance the antiferroelectricity stability but also the breakdown field (Eb). Further investigation reveals that the wider band gap (Eg) and suppression of oxygen vacancy play more important role in increasing Eb of AN-CHTx ceramics. Consequently, an ultrahigh recoverable energy density (Wrec) of 5.4 J/cm3 together with a relatively high energy conversion efficiency (η) of 66% is achieved under an electric field of 300 kV/cm in AN-CHT0.06 ceramics. Meanwhile, this ceramic also exhibits a good thermal stability with Wrec (4.5 J/cm3) and η (69%) over a wide temperature range (25–120 °C) under external electric field of 280 kV/cm. The finding in present work indicates that modulating the band structure and oxygen vacancy of AN-based ceramics may lead to the discovery of new antiferroelectric materials with pronounced energy storage properties.