Stabilizing polar P21ma phase in Bi0.5Na0.5TiO3-Na0.91Bi0.09Nb0.94Mg0.06O3 relaxors by CaTiO3 additive to promote energy storage density, efficiency and discharge rate

Abstract

Eco-friendly Bi0.5Na0.5TiO3 relaxor ferroelectric has attracted considerable attention for pulsed power capacitor applications due to its large saturation polarization. However, high remnant polarization and low breakdown strength (Eb) restrict its application. Herein, linear dielectric CaTiO3 (CT) is introduced into Bi0.5Na0.5TiO3-Na0.91Bi0.09Nb0.94Mg0.06O3 (BNT-NBNM) ceramic to enhance its Eb. Interestingly, CT additive can stabilize polar orthorhombic P21ma phase. As a result, a high recoverable energy density of 6.4 J/cm3 and a high efficiency of 92% at 400 kV/cm as well as an ultrafast discharge rate of 57 ns are obtained in 0.63BNT-0.27NBNM-0.1CT ceramic. Furthermore, temperature dependent Raman spectra reveal that the superior temperature stability of energy storage properties over the temperature span of 30–150 °C is due to insensitive B-O vibration to temperature. The results demonstrate an effective strategy to construct superior and stable BNT-based energy storage materials for pulsed power capacitor applications.