The phase composition, dielectric, and energy storage performance of A-site vacancy modulated BaTiO3 ceramics with Bi(In1/2(Li0.5Ta0.5)1/2)O3 modification

Abstract

The (1-x)Ba_0.94Ce_0.04TiO₃-xBi(In_1/2(Li_0.5Ta_0.5)_1/2)O₃ (BCT-BILT) relaxor ferroelectric ceramic system was explored based on the A-site vacancy design and defect dipole engineering. The impacts of different doping concentrations on the phase composition, dielectric and energy storage performance of the BCT-BILT ceramics were studied and discussed in detail. The pure BCT and 0.95BCT-0.05BILT samples exhibited a mixed crystal structure of tetragonal (T) and pseudo-cubic (PC) phase, while the BCT-BILT samples with x > 0.05 possessed a cubic (C) phase, accompanied by the secondary phases of BaBi₂Ta₂O₉ and BaTa₂O₆. With an increase in the BILT doping concentration, the surface morphologies of the ceramics were continuously modulated, and the dielectric loss had been reduced to 0.001 at 1 kHz, which was beneficial to improve the energy storage properties. Compared to the pure BCT, the breakdown field strength was significantly enhanced owing to the formation of Aurivillius phase BaBi₂Ta₂O₉ and the increased dielectric relaxation. Ultimately, the highest energy storage density of W_rec = 0.7 J/cm³ and high energy conversion efficiency of η = 95 % was realized at the composition of x = 0.05 under a small electric field of 130 kV/cm. Furthermore, the good temperature stability with the ΔW_rec/W_rec30°C < 9 % and Δη/η_30°C < 6.5 % was acquired for the samples with x = 0.20–0.30 in the temperature range of 30–120 °C, owing to the synergistic roles of the defect dipoles, impurities BaBi₂Ta₂O₉, and polar nanoregions (PNRs). The 0.95BCT-0.05BILT ceramic obtains discharge energy density W_dis of 0.35 J/cm³ and fast discharge speed t_0.9 of 312 ns at 60 kV/cm, current density C_D of 255.4 A/cm² and power density P_D of 10.2 MW/cm³ at 80 kV/cm. This work is of guiding significance for designing and optimizing energy storage performance of lead-free relaxors from the perspective of defect building and engineering.