[Bi_0.5(Na_0.4-xLi_xK_0.1)]_0.96Sr_0.04Ti_0.975Ta_0.025O₃ lead-free RELAXOR ceramics with the enhanced recoverable energy density

The high recoverable energy density (W_rec) of 1.83 J/cm³ was achieved at 120 kV/cm by simply introducing 0.050 mol. % Li⁺ ions into the A-site of Bi_0.5(Na_0.4K_0.1)]_0.96Sr_0.04Ti_0.975Ta_0.025O₃ lead-free relaxor ceramics. Bi_0.5(Na_0.4-xLi_xK_0.1)]_0.96Sr_0.04Ti_0.975Ta_0.025O₃ (BNKSTT-100xLi) ceramic samples were prepared by solid-state reaction method. The influence of Li⁺ ions on structure and electrical properties was analyzed in detail. XRD patterns and Raman spectra of these samples were revealed a pure perovskite-type structure. BNKSTT-100xLi ceramics exhibited an obvious relaxor characteristic with the downshift of T_F-R to ambient temperature. J - E loops confirmed the relaxor ferroelectric like nature. Leakage current density was proved to decrease with the increasing Li⁺ ions concentration. At the composition x = 0.050, remnant polarization (P_r) kept steady while maximum polarization (P_max) and breakdown strength (DBS) increased obviously, which was beneficial to the enhancement of recoverable energy density.