The effects of Ti-excess non-stoichiometry on the energy storage performances of BNT-based thin films

In this study, we proposed a novel method of adding large amount of excessive Ti in Bi 0.5 Na 0.5 TiO 3 -based thin film to improve its energy storage density. Ti-excess 0.94Bi 0.5 Na 0.5 Ti x O 3 -0.06BaTi x O 3 (BNBT x , x  = 1.00, 1.05, 1.10, 1.15) thin films were successfully prepared by sol–gel method. It was found that the phase structure of the thin films kept unchanged with the increase of Ti content, and substantial improvements in microstructure and breakdown strength could be obtained by the addition of an excess of Ti in BNBT x thin films, as well as reduced leakage. As a result, improved energy storage density of 34 J/cm 3 and energy storage efficiency of 48% were achieved simultaneously in BNBT 1.15 thin film at a medium electric field of 2400 kV/cm. Furthermore, Ti-excess thin films showed high-dielectric constant with good temperature stability from 25 to 200 °C. These results demonstrate that Ti-excess BNBT x thin film is a potential system for energy storage materials.