Mediating the confliction of polarizability and breakdown electric-field strength in BNST relaxor ferroelectric for energy storage applications

Abstract For relaxor ferroelectric energy-storage capacitors, the breakdown electric-field strength was usually enhanced by sacrificing polarization intensity. In this work, the relaxor ferroelectric Bi0.41Na0.35Sr0.21TiO3 (BNST) has been chosen with the aim to achieve excellent energy storage properties via grain size engineering. By tailoring the grain sizes of BNST relaxor ferroelectric, the fraction of rhombohedral phase was increased, and a medium ferroelectric polarization and high breakdown strength was obtained. The enhancement of energy-storage properties with large recoverable energy density (Wrec = 2.04 J/cm3) and high energy efficiency (ƞ = 82.4%) was simultaneously achieved under a low electric-field (E = 135 kV/cm) with the grain size of 1.04 μm. In addition, the BNST ceramics exhibited good fatigue properties with the variation of Wrec less than 1% over 106 cycles. The grain size engineering greatly increases dielectric breakdown strength because of the denser microstructure and moderate polarization intensity, indicating that it is an effective approach to improve the energy-storage performance in relaxor ferroelectrics.