Phase‐Field Simulations of Tunable Polar Topologies in Lead‐Free Ferroelectric/Paraelectric Multilayers with Ultrahigh Energy‐Storage Performance

Dielectric capacitors are emerging energy-storage components that require both high energy-storage density and high efficiency. The conventional approach to energy-storage enhancement is polar nanodomain engineering via chemical modification. Here, a new approach of domain engineering is proposed by exploiting the tunable polar topologies that have been observed recently in ferroelectric/paraelectric multilayer films. Using phase-field simulations, it is demonstrated that vortex, spiral, and in-plane polar structures can be stabilized in BiFeO3 /SrTiO3 (BFO/STO) multilayers by tailoring the strain state and layer thickness. Various switching dynamics are realized in these polar topologies, resulting in relaxor-ferroelectric-, antiferroelectric-, and paraelectric-like polarization behaviors, respectively. Ultrahigh energy-storage densities above 170 J cm-3 and efficiencies above 95% are achievable in STO/BFO/STO trilayers. This strategy should be generally implementable in other multilayer dielectrics and offers a new avenue to enhancing energy storage by tuning the polar topology and thus the polarization characteristics.