Bi-doping modulation and interface engineering design for synergistic optimization of energy storage performance in SrTiO3/BixBa(1-x)Zr0.35Ti0.65O3/SrTiO3 thin films

Dielectric capacitors are characterized by high power density, fast charge/discharge rates and long cycle life. However, their practical energy storage applications are severely limited by a high remnant polarization ( P r ) and an intrinsically low breakdown field strength ( E b ) To address these issues, SrTiO 3 /Bi x Ba(1- x )Zr 0.35 Ti 0.65 O 3 /SrTiO 3 (STO/B x BZT/STO) ( x  = 0, 0.02, 0.04, 0.06) multilayer ferroelectric films, with SrTiO₃ (STO) as both buffer and capping layers, were fabricated via the sol-gel method. We found that appropriate Bi 3 + doping significantly promoted crystallization and simultaneously induced the formation of defect dipoles, resulting in a dense and uniform microstructure. Meanwhile the bilayer compressive stress from the STO interface layers optimized the domain structure, facilitating a faster response of the polar nanoregions to electric fields. These synergistic effects led to a higher maximum polarization and a lower P r . In particular, the STO/BBZT/STO-0.02 film exhibited excellent overall energy storage performance: under a E b of 4568 kV/cm, it achieved a high recoverable energy storage density ( W rec ) of 41.6 J/cm³ with an energy storage efficiency ( η ) of 71.36%. Notably, after 10 8 cycles of ferroelectric fatigue testing, the variation in W rec was only 8.15%, while maintaining an excellent efficiency ( η = 88.99%). The film also demonstrated good frequency stability (1∼10 kHz) and temperature stability (20∼120 °C). This synergistic optimization strategy holds great promise for providing a new approach to the development of next-generation high-performance dielectric capacitors.