Synergistic effect enhances energy storage properties of BNT-based relaxor ferroelectric thin films

Lead-free thin film capacitors with high energy density and efficiency are promising candidates for pulse power systems in advanced electronic industries due to their low cost, lightweight, and integration development. In this study, 0.6Bi0.5Na0.5TiO3-0.4Sr0.7Bi0.2TiO3+x mol Mn (BNT-SBT-xMn) thin films are fabricated on Pt/Ti/SiO2/Si substrates via sol-gel method. The BNT-SBT-xMn films with perovskite phase possess uniform grain size, well density, and low roughness. The introduction of Mn ions compensates for valence unbalances of A-site vacancy of BNT-based films and forms defective dipoles. Their synergism hinders the transmission of carriers, reduces the leakage current density, and improves polarization and breakdown behavior. Therefore, the BNT-SBT-2% Mn film achieves a high recoverable energy density of 85.35 J/cm3 together with an enhanced energy efficiency of 73.17% under an electric field of 3114 kV/cm. Meanwhile, the BNT-SBT-2% Mn film displays a good frequency (10 Hz-2k Hz), temperature (20–200 °C), and fatigue (1-105 cycles) stability in electrical energy storage properties, suggesting that it would be a promising candidate for the advanced power systems.