Medium electric field-induced ultrahigh polarization response and boosted energy-storage characteristics in BNT-based relaxor ferroelectric polycrystalline ceramics

Abstract

Lead-free dielectric ceramics with a high recoverable energy-storage density (Wrec) and improved efficiency (η) are crucial for the development of pulse power capacitor devices. Although Wrec has been constantly improving, mainly via an increased breakdown electric field strength (Eb), a large driving electric field (>500 kV/cm) increases security risks and consequently increases insulating technology costs. In this work, we present a new (Bi0.5Na0.5)TiO3 (BNT)-based relaxor ferroelectric system, (1−x)(0.75Bi0.5Na0.4K0.1TiO3-0.25SrTiO3)-xBi(Mg0.5Ti0.5)O3 (BS-xBMT), with x ranging from 0.05 to 0.20. BMT disrupts both the A- and B-site long-range ferroelectric order of the ABO3 perovskite-structured BS matrix, induces polar nanoregions, and simultaneously increases Wrec and η. Aided by the viscous polymer process, the Eb with x = 0.15 increased to 270 kV/cm, and a maximum polarization (Pm) of 62 μC/cm2 was attained. A boosted Wrec of 4.82 J/cm3 and a high η of 84.9% were simultaneously obtained, together with good temperature stability from 30 to 140 °C. These results show that BNT-based dielectric ceramics with superior energy-storage properties can be obtained under a medium electric field.