Relaxor properties and breakdown strength of Ta doped Sr0.7Bi0.2TiO3-based lead-free ceramics for energy storage applications

Ferroelectric ceramic capacitors show great potential in pulse power devices for their fast charging-discharging characteristics and immense power density. As a relaxation ferroelectric material, Sr0.7Bi0.2TiO3 has the advantage of high energy storage efficiency. Nevertheless, its low breakdown strength limits its energy storage performance. Herein, Sr0.7Bi0.2Ti(1-1.25x)TaxO(3) (SBT-T) ceramics were synthesized by introducing Ta2O5 with a broad bandgap. On the one hand, the B-site ion disorder enhanced the relaxor behavior of the SBT-T ceramics. On the other hand, the introduction of Ta boosted the impedance and activation energy of the SBT-T ceramics, thus significantly improving their breakdown strength. With the increase in Ta content, the critical electric fields of SBT-T ceramics were monotonically increased from 240 to 370 kV/cm (increased by 54%), and splendid W-rec = 2.33 J/cm(3) and high eta = 91.76% were achieved when x = 0.04 under 290 kV/cm. Additionally, the SBT-0.04T ceramics demonstrated excellent pulse charge-discharge speed (t(0.9) of 81.69 ns) and power density (P-D of 153.39 MW/cm(3)). This research revealed that Ta doping was an effective approach to strengthening breakdown strength, which might provide ideas for improving the energy storage performance of dielectric capacitors.