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

Abstract

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 BiFeO 3 /SrTiO 3 (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.

Antiferroelectric Phase Diagram Enhancing Energy-Storage Performance by Phase-Field Simulations

“…The related research reported that the vortex−antivortex structure was modulated in SrTiO 3 /BiFeO 3 /SrTiO 3 trilayers under an external in-plane strain ε of −3.7 to −2.1%. 39 Such a topological domain structure was also found in the SrTiO 3 / PbTiO 3 superlattice system, induced by gradient energy and elastic energy mainly, in which gradient energy is required to rotate or change the direction or magnitude of polarizations. 40 Additionally, the vortex domain tends to appear at the domain boundary where anisotropy energy is much lower, as shown in Figure 2c.…”

“…The anisotropy controlled by the Landau energy can turn the polarizations into the AFE stripe domain (λ = −2.0, g = 0.3), as shown in Figure S1d. The related research reported that the vortex–antivortex structure was modulated in SrTiO 3 /BiFeO 3 /SrTiO 3 trilayers under an external in-plane strain ε of −3.7 to −2.1% . Such a topological domain structure was also found in the SrTiO 3 /PbTiO 3 superlattice system, induced by gradient energy and elastic energy mainly, in which gradient energy is required to rotate or change the direction or magnitude of polarizations .…”

“…In a word, the gradient energy can tune the periodicity of the antiferroelectric domain structure. Still, if the gradient energy exceeds a critical value, the orderly antiferroelectric domain easily turns into a vortex domain. − …”

Theoretical Understanding of Polar Topological Phase Transitions in Functional Oxide Heterostructures: A Review

“…[184] The dielectric energy storage properties for the polar vortex in BFO-based superlattice is further investigated by Liu et al using the phase-field simulations (Figure 8e). [185] It [165] Copyright 2021, Springer Nature. Emergent chirality for polar vortex as measured.…”

“…e) The dielectric energy storage properties for the polar vortex in BFO based superlattice. Reproduced with permission [185]. Copyright 2022, Wiley-VCH.…”