Electrical Field Driven Structural Evolutions of Polymorphic Nanodomains in Ferroelectric Ba(Zr,Ti)O ₃ 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, we reveal the electrical foeld driven structural evolutions of polymorphic nanodomains in   ferroelectric Ba(Zr_0.2Ti_0.8)O₃ (BZT) films by optical second harmonic generation, along with X-ray diffraction and transmission electron microscopy analyses. The BZT films transform between a remnant state to a charged state with an improved energy efficiency (~ 90%) and a superior fatigue endurance (~ 10% loss under 10⁷ cycles), and a large amount of energy is stored and released in a charge-discharge cycle. An increase of phase segregation is revealed under bipolar 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.

Keywords: Ferroelectric thin film, dielectric capacitor, High-energy-density storage, Domain structure and switching, second harmonic generation