Expanded linear polarization response and excellent energy-storage properties in (Bi0.5Na0.5)TiO3-KNbO3 relaxor antiferroelectrics with medium permittivity

Dielectric materials with both high recoverable energy-storage density Wrec and efficiency η have attracted a lot of attention in recent years. Permittivity plays a crucial role in simultaneously achieving high polarization strength and large applied electric fields for any kinds of dielectric materials, among which antiferroelectric ceramics exhibit giant potentials in energy storage. Adjustment of permittivity has seemed to be more in linear dielectrics, but much less cared about in polar dielectrics so far for high-power energy-storage applications. In this work, a novel lead-free solid solution of (1-x)(Bi0.5Na0.5)TiO3-xKNbO3 was reported to show excellent comprehensive energy-storage performances of Wrec of ~5.2 J/cm3, large η of ~88%, fast discharge rate of t0.9 < 200 ns and outstanding temperature and frequency stability at x = 0.16. The X-ray, Raman spectra and scanning electron microscopy and so on demonstrate that it was basically ascribed to the formation of relaxor antiferroelectric phases with temperature-stable dielectric response and expanded linear polarization response, as well as enhanced dielectric breakdown strength induced by sub-micron grains. Particularly, selection of an appropriately medium permittivity value of about one thousand enables the studied AFE composition bring its superiority into full play in energy-storage properties, as demonstrated by a comparison between Wrec values of most previously-reported lead-free ceramics and theoretically predicted ones for linear dielectrics. These findings achieved in current work would provide an important guidance for compositionally designing high-performance energy-storage dielectrics in terms of modifying dielectric properties and polarization responses, particularly for relaxor antiferroelectrics with linear-like characteristics.