Enhanced Energy Density in Core–Shell Ferroelectric Ceramics: Modeling and Practical Conclusions

Abstract

A microstructure‐level model of the core–shell‐structured ferroelectric ceramics was developed through the voronoi tessellation random construction routine. Assuming the shell is linear dielectric and parameterizing the ferroelectric core with a classical and a modified hyperbolic tangent model, finite element method was applied to solve the resulting systems. Statistics of electric field spatial distribution indicate that increasing applied electric field leads to intensified field fluctuation while this effect is weakened through the incorporation with thicker shell. Energy density extracted from the as‐calculated hysteresis loops possesses an optimal value with regard to the shell fraction. Calculation results show that enhancing the saturation polarization and lowering the remnant polarization of the core, as well as modulating the shell fraction within a favorable range, provide the most effective way to obtain high‐energy‐density ceramics. Reducing the core initial and the shell permittivity benefits the energy efficiency. The underlying mechanisms of the enhanced energy density and reduced energy loss in the core–shell ferroelectric ceramics were discovered to be the trade‐offs between the lowered polarization and the weakened dielectric nonlinearity as a consequence of the dilution and depolarization of the shell. This model can guide the engineering of core–shell‐structured ferroelectric ceramics for energy storage.

High Energy Storage Density and Large Strain in Bi(Zn2/3Nb1/3)O3-Doped BiFeO3–BaTiO3 Ceramics

“…Core-shell structures in FE ceramics are reported to alleviate inhomogeneity of local electric fields and weakens dielectric nonlinearity, resulting in slimmer hysteresis loops. 37 Although the work presented does not conclusively prove the arguments presented by the authors of ref.…”

Grain‐size–dependent dielectric properties in nanograin ferroelectrics

“…On the other hand, due to the hysteretic dielectric feature of the ferroelectric ceramic grains, as shown in the upper part of Figure B, the polarization response during charge and discharge processes are separately considered. A classical hyperbolic tangent function is employed during the initial charge upswing, which is written aswhere P is the polarization under the applied field of E and P s , ɛ 0 , and are the saturation polarization, vacuum permittivity, and the zero‐electric‐field permittivity of ceramic grain, respectively. When combined with the standard constitutive definition D = ɛ 0 E + P , here D represents the electric displacement, and the dielectric permittivity of ceramic grain during the initial upswing can be derived by…”

“…Therefore, a finite element method simulation is adopted in Figure 2B, the polarization response during charge and discharge processes are separately considered. A classical hyperbolic tangent function is employed during the initial charge upswing, [36][37][38] which is written as…”

Large activation energy in aged Mn-doped Sr0.4Ba0.6Nb2O6 ferroelectric ceramics

“…Further analyses on the activation energy of oxygen vacancy diffusion under P-E hysteresis loop measurement are necessary to clarify this consideration. As the polarization is linked to the energy storage density, [56][57][58][59] Fig. 7(i) gives the value of P max ÀP r and the energy storage density aer aging 785 h of all the samples.…”