Phase structure, dielectric and energy storage properties of Na_0.5Bi_0.5TiO₃-BaTiO₃ ceramics with Bi(Mg_2/3Nb_1/3)O₃ modification

Na_0.5Bi_0.5TiO₃ (NBT)-based ceramics are promising lead-free candidates for energy-storage applications owing to their individual crystal structure and phase transition information. However, the high coercive field (E_C) and large remnant polarization (P_r) are detrimental for practical applications. In this work, the composition-dependent phase structure, micromorphology, dielectric and energy storage properties of (1-x)(0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃)-xBi(Mg_2/3Nb_1/3)O₃ (NBBT-100xBMN, x = 0.18, 0.20, 0.22 and 0.25) ternary ceramics were hereby investigated. The addition of BMN facilitates the phase transformation from rhombohedral (R3c) to tetragonal (P4bm), which is beneficial for the enhancement of relaxation behavior, and meanwhile impels the grain growth. Combined with the influence of grain size on breakdown field strength, an optimal recoverable energy storage density (W_rec) of 1.88 J/cm³ with a high energy storage efficiency (η) of 82.15% was achieved in the NBBT-20BMN ceramic composition under the dielectric breakdown strength (DBS) of 150 kV/cm, accompanied by the excellent temperature stability from room temperature to 200 °C. All these manifest that the NBBT-20BMN ceramics have an attractive application prospect in the energy storage field.