Electrical Field Driven Structural Evolutions of Polymorphic Nanodomains in Ferroelectric Ba(Zr,Ti)O3 Films

Abstract Film ferroelectrics possessing large breakdown strength and high energy density hold great promise for compact and efficient power systems. However, it is still unclear how the evolution of their underlying structure engenders their defining energy storage properties. Here, the electrical field‐driven structural evolutions of polymorphic nanodomains in 1400 nm ferroelectric Ba(Zr 0.2 Ti 0.8 )O 3 (BZT) films by optical second‐harmonic generation, along with X‐ray diffraction and transmission electron microscopy analyses are revealed. The BZT films transform between a remnant state to a charged state with an improved energy efficiency (≈90%) and an excellent fatigue endurance (virtually no loss in energy efficiency and ≈25% loss in stored energy after 10 7 bipolar cycles @ 1.5 MV cm −1 maximum electric field). Phase separation is significantly increased after charge‐discharge cycles. The performance is attributed to ultra‐adaptive polymorphic nanodomains, which effectively accommodate the concurring elastic and electrical stress fields during electrical switching.