Achieving Remarkable Energy Storage Performances under Low Electric Field in Bi_0.5N_0.5TiO₃-SrTiO₃-Based Relaxor Ferroelectric Ceramics via a Heterostructure Doping Strategy

The rapid growth of the electronics industry and increasing concern about environmental issues present great demands for lead-free dielectric ceramic capacitors with remarkable energy storage performances (ESPs). Lead-free perovskite ferroelectric and antiferroelectric systems are deemed as the most promising candidates, and homostructure linear dielectric doping is a widely used strategy to boost ESPs. However, the heavy doping of a linear dielectric usually leads to a great reduction of the polarization, for which an extremely high electric field is needed to achieve a large energy storage density (Wrec). In this study, a Bi0.5N0.5TiO3-SrTiO3 (BNT-ST)-based relaxor ferroelectric system was designed via a heterostructure doping strategy in which a tetragonal tungsten bronze ferroelectric phase Sr2NaNb5O15 (SNN) was introduced into the perovskite matrix. It was found that a small SNN heterostructure doping amount could effectively enhance the relaxor behavior of the BNT-ST ceramic and depress the remnant polarization, while keeping a large maximum polarization. Moreover, the introduction of the tungsten bronze ferroelectric phase obviously decreased the grain size (G) of the BNT-ST ceramic, giving rise to an improved electric breakdown strength (Eb). Finally, a remarkable Wrec of 5.22 J/cm3 and excellent efficiency (η) of 93.87% were attained under a low electric field of 340 kV/cm, which make the Bi0.5N0.5TiO3-SrTiO3-xSr2NaNb5O15 (BNT-ST-xSNN) ceramic system a promising choice for the dielectric energy storage field. These results demonstrate that the heterostructure doping strategy might be a feasible method to develop lead-free perovskite dielectric ceramics with remarkable ESPs under low electric fields.