Decreasing polar-structure size: Achieving superior energy storage properties and temperature stability in Na0.5Bi0.5TiO3-based ceramics for low electric field and high-temperature applications

It is a grand challenge to achieve high energy density (W) and efficiency (η) simultaneously under a low electric field (LE) to obtain new high energy storage capacitors. Similar to anti-ferroelectrics, the (1-x)NBT-xBaMg_1/3Nb_2/3O₃ relaxor material exhibits a non-linear dependence on electric field, which is caused by a reversible field-induced phase transition. This leads to high W (2.37 J/cm³) and η (81.5 %) under a LE of 155 kV/cm, which makes it superior to other bulk ceramics. Combining large polarizability of Ba²⁺ in A-site and local structural heterogeneity on the B-site by Mg_1/3Nb_2/3⁴⁺, enhanced relaxor behavior and decreased polar-structure size were induced in (1-x)NBT-xBaMg_1/3Nb_2/3O₃ ceramics. The permittivity, nevertheless, stays high at ～2273±15 %. Furthermore, the electrical properties become stable in a wide temperature range from 44?396 °C for the sample with x=0.15. In addition, high current density/C_D (450 A/cm²), power density/P_D (23 MW/cm³) and discharge density/W_D (0.57 J/cm³) were realized tested with pulse discharge testing. Our work will provide a development guidance for dielectric energy storage ceramics at low field and high fields with excellent temperature stability.