Enhanced Energy Storage Performance in BNKT-Based Lead-Free Thin Films at Low Electric Fields

Dielectric capacitors with high energy storage performance are crucial for electronic devices, yet they face the critical challenge of achieving such performance under low electric field strengths. Although relaxor ferroelectric thin films typically exhibit high energy storage performance, they generally suffer from a lower maximum polarization ( P max ). Furthermore, achieving high recoverable energy storage density ( W rec ) commonly requires elevated electric fields, which may accelerate the degradation of electronic components. To address this challenge, we designed and fabricated lead-free (1– x )[0.6 Bi 0.5 (Na 0.8 K 0.2 ) 0.5 TiO 3 -0.4SrTiO 3 ]- x LaAlO 3: Mn (abbreviated as BNKT-ST- x LA: Mn) multicomponent ferroelectric thin films. The results indicate that LA doping significantly improves the surface morphology of the thin films and enhances their relaxor behavior. Consequently, at x = 0.05, a high polarization difference (Δ P = 68.39 μC/cm 2 ) along with superior energy storage performance ( W rec = 34.33 J/cm 3, efficiency η = 70.1%) are achieved under an electric field of approximately 1500 kV/cm. XPS results reveal that La 3+ and Al 3+ codoping can enhance the energy storage performance of the thin films by modulating the concentration of oxygen vacancies. These findings indicate that such lead-free ferroelectric thin films not only offer valuable insights for achieving high energy storage performance under low electric fields but also present a strategy for realizing anomalously enhanced P max in the relaxor state.