关键词: BNT基陶瓷, 弛豫铁电体, ZnNb₂O₆, 介电性能, 铁电性能, 储能特性

Abstract: In this paper, 0.7(Na_0.5Bi_0.5)TiO₃-0.3(Sr_0.7Bi_0.2)TiO₃-xZnNb₂O₆ (abbreviated as BNT-SBT-xZN, where x=0.5%, 1.0%, 1.5% and 2.0%, molar fraction) ceramics were prepared by the solid-state reaction method. The effect of ZnNb₂O₆ doping on the structure and properties of BNT-based ceramic materials was studied. The results show that, BNT-SBT-xZN ceramics doped with a small amount of ZnNb₂O₆ (x=0.5%) have pure perovskite structure with compact microstructure and no second phase. At room temperature, they are typical relaxor ferroelectrics (dispersion index γ>1.7). For all unpoled and poled BNT-SBT-xZN ceramics of x=0.5%, the transition temperature of ferroelectric-relaxation (T_R-E) is lower than room temperature, while T_R-E is below 100 ℃, which denotes the dielectric anomalous associated with thermal relaxation of polar nano regions (PNRs) in rhombohedral (R3c) and tetragonal (P4bm) symmetrical structure. When the content of ZnNb₂O₆ increases, the ergodic relaxor state gradually plays a dominant role, maximum polarization (P_max) and remanent polarization (P_r) both show a decreasing trend. BNT-SBT-xZN ceramics with x=0.5% have high P_max, low P_r and large ΔP, resulting in excellent energy storage characteristics and frequency and temperature stability with P_max of 44.7 μC/cm², P_r of 12.4 μC/cm², ΔP of 32.3 μC/cm², energy density (W₁)of 1.066 J/cm³, energy storage efficiency (η) of 48.68% under 110 kV/cm. Moreover, discharge energy density W_d, maximum discharge current I_max, current density C_D and power density P_D of 0.60 J/cm³, 45.33 A, 1 443 A/cm² and 72.2 MW/cm³ are obtained at room temperature and 100 kV/cm, respectively.

Key words: BNT-based ceramics, relaxor ferroelectric, ZnNb₂O₆, dielectric property, ferroelectric property, energy storage characteristic