Achieving excellent energy storage properties in lead-free ceramics via competing FE/AFE phase coexistence

Dielectric capacitors are widely utilized in large-scale power systems, including applications in medical and military fields. However, their relatively low energy storage density limits further advancements in miniaturization and integration. Therefore, improving the energy storage density of dielectric capacitors is of paramount importance. In this work, novel lead-free Na_0.70Sr_0.15Nb_0.75Ta_0.25O₃ (NSNT) ceramics were designed, which exhibit a unique combination of relaxor ferroelectric (FE) N phase and stabilized antiferroelectric (AFE) P phase, as confirmed through local structural analysis. The competing FE/AFE phase coexistence is attributed to the discrepancy in ion valence and radius. As a result, the NSNT ceramics demonstrate exceptional energy storage performance, featuring a recoverable energy density (W_rec) of 10.45 J/cm³ and an energy efficiency (η) of 83.0 % at 850 kV/cm, along with excellent stability. These outstanding energy storage properties not only confirm the promising application prospects of NN-based ceramics with competing FE/AFE phase coexistence, but also provide an innovative approach for advancing high-performance ceramic capacitors.