Lead-free bismuth sodium titanate (BNT)-based ceramics have attracted strong attention as environmentally benign dielectric materials for high-efficiency electrostatic energy-storage capacitors. A key challenge is that pristine BNT typically exhibits large hysteresis, high remnant polarization, and limited dielectric reliability, which restrict recoverable energy storage and efficiency under practical electric fields. Here, we present a focused mini-review of recent studies to clarify how composition design, phase boundary tuning, defect chemistry, and microstructural control collectively enable slim or pinched polarization-electric field (P-E) behavior and improved energy-storage functionality in BNT-related bulk ceramics. The reviewed outcomes consistently show that stabilizing relaxor states governed by polar nanoregions (PNRs), often via solid-solution engineering and secondary relaxor/antiferroelectric-like incorporation, suppresses irreversible switching and reduces hysteresis loss, while densification and grain-size control enhance electrical homogeneity and breakdown strength. In addition, defect-mediated tuning of oxygen vacancy-related complexes is highlighted as an independent lever to control relaxor ergodicity and polarization reversibility, providing a complementary route to slim-loop optimization. These insights are expected to guide integrated design strategies that couple phase/relaxor-state engineering with defect and microstructure optimization, accelerating the development of reliable, temperature-robust, lead-free dielectric capacitors based on BNT-related ceramics.

We investigated the dielectric and mechanical properties of ceramic polymer composite xBNT - (1-x)LCP (x= 0, 10, 20, 30, 40 vol.%). The disk shaped BNT (BaNd2Ti4O12) - LCP (liquid crystal polymer) composite samples were prepared by compression molding method. With increasing the BNT content in composites from 10 to 40 vol.%, the dielectric constant increased but the dielectric loss as well as bending strength of composites reduced. These composites were well described with modified Lichtenecker`s model having k = 0.392 and 0.303 for the first and second ball milled BNT filled composites, which means that the BNT filler in composites are well dispersed. The dielectric constant of the composite comprised of the second milled BNT (D50 = 1.39 um) was higher that of the composite of the first milled BNT (D50= 2.45 um), which seems to be related with the different particle size and dispersion of BNT fillers in LCP matrix. The bending strength of the composite containing the second milled BNT was superior to that of the composite of the first milled BNT.

In this study, piezoelectric and dielectric properties of the (Na0.5K0.5)NbO3-(1-x)(Bi0.5Na0.5)TiO3- xBaTiO3 [NKN-(1-x)BNT-xBT] ceramics were investigated. The lead-free NKN-(1-x)BNT-xBT ceramics were fabricated by a conventional mixed oxide method. The results indicate that the addition of BaTiO3 significantly influences the sintering, microstructure, phase transition and electrical properties of NKN-BNT ceramics. A gradual change in the piezoelectric and dielectric properties was observed with the increase of BT contents. The dielectric constant, piezoelectric constant (d33) and electromechanical coupling factor (kp) increased at the morphotropic phase boundary (MPB). The d33=184 pC/N, kp=0.38, dielectric constant=1455 with dielectric loss value of less than 1% were obtained for the NKN-0.95BNT-0.05BT ceramics sintered at 1150℃ for 2h. These results demonstrate that the NKN-(1-x)BNT-xBT ceramics is an attractive candidate for lead-free piezoelectric materials.