Ultra-High Energy Storage Performance in BNT-based Ferroelectric Ceramics with Simultaneously Enhanced Polarization and Breakdown Strength

BNT (Bi0.5Na0.5TiO3)-based ferroelectric ceramics have drawn much attention in energy storage applications due to the high saturation 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. A multivalent element (Mn) is adopted in this work to prevent the reduction of Ti4+ and thus enhance the polarization and breakdown strength simultaneously. Various contents of MnO2-doped 0.76Bi0.5Na0.5TiO3–0.04SrZrO3–0.2NaNbO3 (BNTSZNN) ceramics were prepared by the ramp-to-spike sintering method. As the content of MnO2 increases, the reduction of Ti4+ is effectively decreased, inhibiting the degradation of ferroelectricity and decreasing the leakage conductance. As a result, an ultra-high discharge energy density of 7.05 J/cm3 is achieved in the BNTSZNN-0.15MnO2 ceramic at 387 kV/cm. Importantly, the BNTSZNN-0.15MnO2 ceramic shows excellent temperature stability. The change of the discharge energy density between 30 and 160 °C is less than ±4% under the applied field of 120 kV/cm. Additionally, the variation in the capacitance of the BNTSZNN-0.15 MnO2 ceramic is less than ±15% over the temperature range from −58 to 450 °C, with a high room-temperature dielectric permittivity of 1507. All the above characteristics indicate the potential of BNTSZNN-0.15MnO2 as a high-temperature and high-voltage ceramic dielectric.