Achieved high energy density and excellent thermal stability in (1−x)(BiNa)BaTiO−xBi(MgTi)O relaxor ferroelectric thin films

In this work, lead-free (1−x)(BiNa)BaTiO−xBi(MgTi)O (abbreviated as BNBT-xBMT, x = 0.3, 0.4, 0.5 and 0.6) thin films were prepared on Pt/Ti/SiO/Si substrates using sol–gel method. The microstructures, dielectric, and energy storage properties were investigated. The results showed that the addition of BMT disrupted the long-range ferroelectric order and enhanced the relaxor behavior of BNBT-xBMT thin films. In addition, the leakage current density of thin films was also reduced by the doping of a moderate amount of BMT. A high recoverable energy density of 34.36 J/cm with an efficiency of 56.63% was achieved in the BNBT-0.5BMT thin film under the electric field of 2149 kV/cm. Furthermore, BNBT-0.5BMT thin film exhibited superior stability in the temperature range of 30 °C–145 °C and frequency range of 500 Hz–5 kHz, as well as long-term fatigue durability after 1 × 10 cycles. These results suggest that BNBT-0.5BMT thin film may be a promising material for lead-free dielectric energy storage applications.