Structure and electric properties of sandwich-structured SrTiO3/BiFeO3 thin films for energy storage applications

Sandwich-structured SrTiO3/BiFeO3/SrTiO3 (ST/BF) thin films were prepared via a sol-gel method for energy storage applications. The thin films demonstrated good frequency stability of the dielectric constant within the measured frequency range, low dielectric loss and broad capacitance-temperature variation (25 degrees C-200 degrees C, Delta C/C (25 degrees c)<=+/- 6.0%). Through BF layer insertion modulation, the crystallization quality and energy storage density of ST/BF thin films significantly increased in comparison to ST films. In addition, with the increase thickness of BF layers, the breakdown strength and energy storage density decreased. The maximum recoverable energy storage density (U-rec of 40.69 J/cm(3)) with an efficiency of 44.7% at 2.06 MV/cm was obtained within this system. Moreover, compared to simple tri-layered thin films, the U-rec value of the thin films with more interfaces was enhanced to 80%. The results indicate that sandwich-structured ST/BF thin films are a cost-effective, potential more efficient option for energy storage fields. (C) 2018 Elsevier B.V. All rights reserved.