High Energy Storage Performance and Large Electrocaloric Response in Bi 0.5 Na 0.5 TiO 3 -Ba(Zr 0.2 Ti 0.8 )O 3 Thin Films.

With regard to the global energy crisis and environmental pollution, ferroelectric thin films with unique polarization behavior have garnered considerable attention for energy storage and electrocaloric refrigeration. Herein, a series of (1 - x )Bi 0.5 Na 0.5 TiO 3 - x Ba(Zr 0.2 Ti 0.8 )O 3 ( x = 0.3-0.9; (1 - x )BNT- x BZT) films were fabricated on Pt(111)/Ti/SiO 2 /Si substrates. Incorporating BZT can tune the polarization behavior and phase transition temperature of BNT. A high recoverable energy density ≈ 82 J cm -3 and optimized efficiency ≈ 81% were realized for the (1 - x )BNT- x BZT thin film with x = 0.7. The thin film exhibits excellent stability in energy storage performance, a wide working frequency range (0.5-20 kHz), a broad operating temperature window (20-200 °C), and reduplicative switching cycles (10 7 cycles). In addition, the 0.5BNT-0.5BZT film exhibits a desirable electrocaloric effect with a large adiabatic temperature change (Δ T ≈ -22.9 K) and isothermal entropy change (Δ S ≈ 33.4 J K -1 kg -1 ) near room temperature under a moderate applied electric field of 2319 kV cm -1 . These remarkable performances signify that the (1 - x )BNT- x BZT system is a promising multifunctional electronic material for energy storage and solid-state cooling applications.