Effect of Sr Doping on the Energy Storage Performance of Ferroelectric BaZr_0.35Ti_0.65O₃ Thin Films

Ba1–xSrxZr0.35Ti0.65O3 (x = 0, 0.025, 0.05, 0.075, 0.1) ferroelectric thin films were fabricated on Pt/Ti/SiO2/Si substrates by the sol–gel method, and effects of Sr ion doping concentration on the microstructure, breakdown field strength, and energy storage properties were studied. When the Sr doping content was 0.075, a high breakdown field strength EBD of 5.58 MV/cm was obtained, 55% higher than that of the BaZr0.35Ti0.65O3 film. This enhancement is attributed to the decline in the ionic radii of the Sr-substituted Ba grains, which increases the bonding force between the cation and oxygen ions. Furthermore, the oxygen vacancies were inhibited, contributing to a lower leakage current (4.31 × 10–8 A/cm2). Owing to the enhancement of breakdown field strength, the films obtain a higher energy storage density (Wrec = 44.61 J/cm3) with a significant efficiency (η = 91.9%). In addition, the films demonstrate great frequency stability (500 Hz–20 kHz). These noteworthy performances demonstrate that these ferroelectric films have promising applications in the domain of energy storage.