Effect of Sr doping on the energy storage performance of BaBi4Ti4O15 ferroelectric thin films

Ba_1−xSr_xBi₄Ti₄O₁₅ (BBST) ferroelectric thin films (x = 0, 0.025, 0.05, 0.075, 0.1) were prepared on Pt/Ti/SiO₂/Si substrates by sol–gel method. The effects of Sr doping on the microstructure, breakdown field strength (BDS), and energy storage performance of BaBi₄Ti₄O₁₅ (BBT) thin films were investigated. Since the radius of Sr ion (1.44 Å) is smaller than that of Ba ion (1.61 Å), the diffraction peak of the material gradually shifts to a higher angle after doping, the grain size decreases, and the surface compactness of the film increases. In addition, the doping reduces the concentration of oxygen vacancies, so that the leakage current is reduced to 1.59 × 10^–7 A/cm² for x = 0.075 and the BDS reaches 3.23 MV/cm, which is significantly improved by 51.64% compared with the undoped sample. Due to the significant improvement of the BDS, the film obtained higher energy storage density (W_rec = 28.2 J/cm³) and energy storage efficiency (η = 80.36%). The above performance advantages indicate that such ferroelectric thin films have great application potential in the field of energy storage.