Effects of Fe3+ doping on electrical properties and energy-storage performances of the (Na0.85K0.15)0.5Bi0.5TiO3 thick films prepared by sol-gel method

The immense potential of dielectric capacitor for use in energy-storage applications has propelled much recent research and development. Here, we prepared a kind of lead-free ferroelectric thick films of Fe-doped (Na0.85K0.15)0.5Bi0.5TiO3 (NKBT-Fex, x = 0, 0.01, 0.02 and 0.04). The effects of Fe3+ contents on the microstructure, dielectric properties and energy-storage performances of NKBT thick films were studied in detail. The studies on complex impedance spectroscopic were also carried out for NKBT-Fe0.02 thick film at different temperature from 100 Hz to 1 MHz. By Fe doping, the leakage current of the NKBT-Fex thick films was greatly reduced, while the breakdown strength (BDS) and the difference between the maximum polarization and remanent polarization were enhanced. These characteristics lead to excellent energy-storage performances with good temperature and frequency stability. In particular, a maximum energy-storage density (W) of 33.3 J/cm3 with an efficiency (η) of 51.3% was achieved in the NKBT-Fe0.02 thick film. These results open up a promising feasible route to enhance the energy-storage performances by properly element doping.