Dielectric Stability and Energy-Storage Performance of BNT-Based Relaxor Ferroelectrics through Nb⁵⁺ and Its Excess Modification

The ever-increasing development of compact electronic equipment consumption impels us to design lead-free high-performance dielectric energy-storage materials. Herein, the dielectric and polarization mechanism of BNT-BT-BSTN lead-free relaxors with slim polarization hysteresis loops is investigated through B-site modulation. Substitution by stoichiometric and excessive Nb content is proposed to hinder the oxygen vacancies and reinforce the insulation. Complex impedance spectroscopy shows that all compositions possess n-type dominant conduction behavior. The generation of oxygen vacancies and Ti reduction can be further restricted, caused by the excessive Nb content, leading to the increased dielectric resistivity. Interestingly, simultaneous improvement of energy-storage density (2.07 J/cm3) and efficiency (94.5%) is achieved at a relatively low electric field at the high dopant concentration as a result of the fascinating enhancement in polarization, which may be attributed to the impurity or distorted phase caused by Nb excess. The enhanced stability against dielectric and energy-storage performance is also obtained. All these features guarantee the promising prospects of application for BNT-based dielectrics.