Energy storage properties of Mn-modified (Na0.2Bi0.2Ca0.2Sr0.2Ba0.2)TiO3 high-entropy relaxor-ferroelectric ceramics

It remains a huge challenge to enhance the energy-storage density (ESD) and efficiency (ESE) of Pb-free dielectrics for ES applications. The perovskite structured high-entropy ceramics are regarded as a promising candidate for pulsed power system devices because of their interesting properties originating from high-entropy effect. Nevertheless, the main drawback of high-entropy ferroelectric materials is their relatively low electric breakdown strength. In this study, MnCO3, as an additive, was designed to improve the insulation resistance of (Na0.2Bi0.2Ca0.2Sr0.2Ba0.2)TiO3-x wt% MnCO3 (NBCSBT-xMn) high-entropy relaxor-ferroelectric ceramics via a conventional solid-state technique. The as-prepared pellets have a well-crystallized pseudo-cubic perovskite structure. Excess Mn content can decrease the grain size and dielectric loss and enhance the relaxation factor, active energy and maximum dielectric constant (εm)-dependent temperature (Tm). The ES performance first increased and then decreased. Consequently, the composite ceramics, with × = 0.5, demonstrated an excellent ESE (η) of 70.2% and a high recoverable ESD (Wrec) of 1.56 J/cm3 at 160 kV/cm because of the increased relaxation factor and reduced defect concentration and the adequate grain size. These properties suggest that novel Mn-doped NBCSBT ceramic is attractive for ES applications.