Insight into the Structure Evolution and Performance Optimization of Bi0.5Na0.5TiO3-Based Ceramics for Energy Storage Application

The excellent temperature stability and high saturation polarization of Bi_0.5Na_0.5TiO₃ (BNT) make it a promising candidate for energy storage capacitors. However, its disadvantages, such as low breakdown strength, high remnant polarization, and a complex sintering process, limit its further development. To address this, (1 - <i>x</i>) Bi_0.5Na_0.5TiO₃-x Sr(Mg_1/3Nb_2/3)O₃ ceramics were fabricated, where ion doping was employed to modify the domain structure, reduce the grain size, and improve the energy storage performance. With the increase in dopant concentration, the evolution from long-range-ordered ferroelectric micro-domains into short-range-ordered randomly oriented polar nanoregions (PNRs) was revealed, as demonstrated by XRD and Raman spectroscopy. This resulted in a diffuse phase transition peak and a significant reduction in remnant polarization. However, the saturation polarization also decreased. Finally, the optimal energy storage performance was achieved at a medium dopant concentration (<i>x</i> = 0.10), accompanied by reduced grain size and a dense microstructure. This composition exhibited a discharged energy density of 1.64 J/cm³ at a low electric field of 150 kV/cm, representing a notable improvement over pure BNT, which showed a highly lossy P-E loop and a discharged energy density of only 0.14 J/cm³ at the same electric field.