Phase-field simulation of domain size effect on dielectric and piezoelectric responses in K0.5Na0.5NbO3 epitaxial thin films with superdomain structures
Phase-field simulation of domain size effect on dielectric and piezoelectric responses in K0.5Na0.5NbO3 epitaxial thin films with superdomain structures
复制标题
DOI：
10.1016/j.actamat.2023.118777
复制
发表时间：
2023-02
期刊：
影响因子：
9.4
通讯作者：
Menghan Zhou;Bo Wang;Kun Peng;Han Liu;Long-Qing Chen;C. Nan
中科院分区：
文献类型：
--
作者：
Menghan Zhou;Bo Wang;Kun Peng;Han Liu;Long-Qing Chen;C. Nan
二十多年来，人们对介观铁电域对域工程块体压电晶体中宏观介电和压电响应的尺寸效应进行了广泛研究。然而，人们对铁电外延薄膜中的畴尺寸效应知之甚少，特别是对于由低对称性铁电相组成并表现出分层超畴结构的薄膜。在此，利用相场模拟，我们系统地评估了铁电 K 0.5 Na 0.5 NbO 3 外延薄膜中两种超畴结构的有效面外介电系数和压电系数 κ 33* 和 d 33* 作为畴周期的函数。在一种超域结构中，我们发现通过将域周期调整几十纳米，可以实现κ 33* 增加超过70％和d 33* 增加近20％。当域周期沿不同横向方向变化时，会发现不同的行为，这表明薄膜中存在各向异性域尺寸效应。通过分析每个畴变体和畴壁的局部介电和压电响应，我们揭示了畴尺寸效应是由畴内面外极化的变化决定的。此外，我们还证明了通过调节失配应变和温度以接近多态相边界来增强域尺寸效应，这表明通过掺杂和应变工程可以调节尺寸效应。我们的结果揭示了低对称性铁电外延薄膜中介电和压电响应的多模域尺寸依赖性，这意味着域尺寸工程可用于调整薄膜铁电体的宏观性能，类似于其块体对应物。
Size effects of mesoscale ferroelectric domains on the macroscopic dielectric and piezoelectric responses in domain-engineered bulk piezocrystals have been extensively studied for more than two decades. However, less is known about the domain size effects in ferroelectric epitaxial thin films, especially for films consisting of low-symmetry ferroelectric phases and exhibits hierarchical superdomain structures. Herein, using phase-field simulations, we systemically evaluate the effective out-of-plane dielectric and piezoelectric coefficients, κ 33* and d 33*, as a function of the domain periods for two types of superdomain structures in ferroelectric K 0.5 Na 0.5 NbO 3 epitaxial thin films. In one type of the superdomain structures, we find that more than 70% increase of κ 33* and nearly 20% increase of d 33* can be achieved by tuning the domain period by a few tens of nanometers. Dissimilar behaviors are found when the domain period varies along different lateral directions, suggesting anisotropic domain size effects in thin films. By analyzing the local dielectric and piezoelectric responses from each domain variants and domain walls, we reveal that the domain size effect is governed by the variation of out-of-plane polarization inside the domains. Moreover, we also demonstrate enhanced domain size effects by modulating the misfit strains and temperature to approach the polymorphic phase boundaries, suggesting tunability of the size effect by doping and strain engineering. Our results reveal multimodal domain size dependence of dielectric and piezoelectric responses in low-symmetry ferroelectric epitaxial thin films, implying that domain size engineering can be used to tune macroscopic properties of thin-film ferroelectrics, similar to their bulk counterparts.