Abnormal Electromechanical Property of Nonlinearly Graded Lead‐Free Ferroelectric Thin Films
Abnormal Electromechanical Property of Nonlinearly Graded Lead‐Free Ferroelectric Thin Films
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DOI：
10.1002/adts.202100370
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发表时间：
2021-11
影响因子：
3.3
通讯作者：
L. Lich;T. Bui;T. Shimada;T. Kitamura;Hue Dang Thi Hong;Trong‐Giang Nguyen;V. Dinh
中科院分区：
文献类型：
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作者：
L. Lich;T. Bui;T. Shimada;T. Kitamura;Hue Dang Thi Hong;Trong‐Giang Nguyen;V. Dinh
基于金兹堡-朗道理论建立了非线性梯度铁电薄膜的相场模型。通过仿真结果与现有实验数据的对比，验证了所建立的相场模型的正确性。通过相场仿真，系统地研究了梯度指数对极化场和机电响应的影响。在由Ba 1−x$ {1-x}$ SrxTiO3制成的非线性梯度铁电薄膜中，研究了异常大的机电响应，其中SrTiO3摩尔分数根据幂律关系随薄膜厚度变化。此外，在梯度铁电薄膜中可以稳定较大的极化梯度，通过控制薄膜的梯度指数可以控制极化的大小和梯度。薄膜中较大的极化梯度使其极化场更容易受到外界激励，从而显著提高了其机电性能。确定了使机电响应最大化的最优梯度指标。此外，考虑梯度薄膜的能量特性表明，随着薄膜梯度指数的增加，储能密度和充放电效率均增加。
A phase field model for nonlinearly graded ferroelectric thin films is developed based on the Ginzburg–Landau theory. The developed phase field model is validated by comparing simulated results and available experiment data. Via phase field simulations, effects of gradient index on polarization field and electromechanical response are systematically investigated. Anomalously large electromechanical responses are explored in nonlinearly graded ferroelectric thin films made of Ba 1−x$_{1-x}$ SrxTiO3, where SrTiO3 mole fraction varies across the film thickness according to power‐law relationships. In addition, a large gradient of polarization can be stabilized in graded ferroelectric thin films, where both magnitude and gradient of polarization can be manipulated by controlling the gradient index of thin films. The remarkable enhancement of electromechanical properties originates from the large gradient of polarization in thin films, which makes the polarization field more susceptible to external excitation. An optimal gradient index for maximizing the electromechanical response is also identified. Furthermore, a consideration of energy properties of graded thin films suggests that both energy storage density and charge–discharge efficiency increase with increasing gradient index of thin films.