162 / 2022-02-12 18:14:10

High-Performance BNT-Based Ferroelectric Ceramics With Simultaneously Enhanced Polarization and Breakdown Strength

high energy storage,high polarization,high breakdown strength,temperature stability

（7）矿物与先进能源材料 > 8. 新型能源材料

ABSTRACT:BNT(Bi_0.5Na_0.5TiO₃)-based ferroelectric ceramics have drawn much attention in energy-storage field due to the high polarization and good temperature stability. However, the reduction of Ti⁴⁺ caused by the volatilization of Bi and Na elements during high-temperature sintering is a huge problem. Multivalence element (Mn) is adopted in this work to prevent the reduction of Ti⁴⁺, and thus enhance the polarization and breakdown strength simultaneously. Various content of MnO₂ doped (0.95Bi_0.5Na_0.5TiO₃-0.05SrZrO₃)-0.2NaNbO₃ (BNTSZNN) ceramics were prepared by the Ramp-to-spike sintering method. The existence of Ti³⁺, confirmed by the X-ray photoelectron spectroscopy (XPS), proves the reduction of Ti⁴⁺. As the content of MnO₂ increases, the content of Ti³⁺ is effectively decreased, reducing the degradation of ferroelectricity and leakage conductance. As a result, an ultra-high discharge energy density (W_rec) of 7.05 J/cm³ is achieved in the BNTSZNN-0.15MnO₂ ceramic at 387 kV/cm. Importantly, the BNTSZNN-0.15MnO₂ ceramic system behaves quite excellent temperature stability both in energy-storage and capacitance field. The variation in the discharge energy density (W_rec) is less than ±4% in the temperature range from 30 °C to 160 °C under the applied field of 120 kV/cm. Additionally, the variation in the capacitance (or dielectric permittivity) of the BNTSZNN-0.15 MnO₂ ceramic is less than ±15% over the temperature range from -55 °C to 450 °C, with a high room temperature dielectric permittivity of 1507. All the above characteristics indicate the potential of BNTSZNN-0.15MnO₂ as high-temperature and high-voltage ceramic dielectrics.

KEYWORDS: anti-reduction, energy storage, high polarization, high breakdown strength, temperature stability