Influence of Thickness on Dielectric Energy Storage of Sol-Gel Prepared Flexible BZT - NBT Films on Mica

As emerging sectors like new energy and flexible electronics increasingly require high-performance flexible energy storage devices, the development of lead-free inorganic dielectric films that exhibit superior energy storage capabilities and mechanical flexibility has emerged as a key area of research. In the present study, lead-free 0.94 BaZr₀.₂Ti₀.₈O₃ - 0.06 Na₀.₅Bi₀.₅TiO₃ (BZT - NBT) dielectric energy storage films were successfully prepared on flexible fluorophlogopite (Mica) substrates using a sol-gel. A systematic examination was conducted on how film thickness (80, 110, 150, and 200 nm) influences microstructure, electrical characteristics, and energy storage capabilities. Among all the specimens, the 110 nm-thick film exhibits the best overall performance: it has a high breakdown strength (E_b)of 2157 kV/cm, a maximum recoverable energy storage density (W_rec) of 8.38 J/cm³, and an energy storage efficiency (η) of 96.61%. Moreover, this film shows remarkable stability under harsh conditions, including thermal stability (25–200°C), resistance to fatigue (10⁷ charge-discharge cycles), and bending durability (10⁴ cycles), with only slight changes in W_rec and η. These results underscore the significant potential of flexible BZT - NBT films on Mica substrates for use in next-generation flexible energy storage systems, offering useful perspectives for the optimization of inorganic dielectric films.