High energy storage density and efficiency in (Bi0.5Na0.5)0.94Ba0.06TiO3-based ceramics with broadened and flattened dielectric peaks

Abstract

Currently, Bi0.5Na0.5TiO3-based lead-free ferroelectrics have attracted considerable attention as one of the promising candidates for dielectric materials due to their large spontaneous polarization, environmental friendliness and low cost. However, their poor energy density hinder the practical application of the materials. Herein, a novel ceramic of (1-x) (0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-x(0.96NaNbO3-0.04CaSnO3) (BNBT-xNNCS) has been developed by the solid solution of antiferroelectric NaNbO3–CaSnO3 into ferroelectric Bi0.5Na0.5TiO3–BaTiO3 and the microstructure and electrical properties of the material have been systematically investigated. All the ceramics are lied within the coexistence zone of tetragonal (T) and rhombohedral (R) phases, ensuring to the large polarizations of the materials. Importantly, the introduction of NaNbO3–CaSnO3 shifts dielectric peaks at Ts towards room temperature and simultaneously broadens and flattens the dielectric peaks, destroying the ferroelectric long-range order of ferroelectric domains and inducing the generation of polar nanoregions (PNRs) to reduce the remanent polarization. As a result, the prominent energy storage properties with the charge energy storage density (Wtot) of 1.86 J/cm3, recoverable energy density (Wrec) of 1.64 J/cm3 and energy storage efficiency (η) of 88.23% are obtained in the BNBT-xNNCS ceramics with x = 0.20 (BNBT-20NNCS) under a comparatively low electric field strength of 149 kV/cm, accompanying with superior frequency (ΔWrec ≤ 3%, Δη ≤ 3%, 30–90 Hz) and thermal stability (ΔWrec ≤ 10%, Δη ≤ 10%, 25–175 °C).