Zhang Yongkang, Yan Zhaonan, Liu Shuhai, Qin Yong
Institute of Nanoscience and Nanotechnology, School of Materials and Energy, Lanzhou University, Lanzhou, Gansu, 730000, China.
MIIT Key Laboratory of Complex-field Intelligent Exploration, Beijing Institute of Technology, Beijing, 100081, China.
Adv Mater. 2025 Jul 18:e01160. doi: 10.1002/adma.202501160.
Flexoelectricity is enabled by symmetry in all materials. However, flexoelectric material application is limited by the normally low charge density produced in bulk materials. In this study, a universal strategy involving a macroscopic symmetry design is proposed to enhance the flexoelectricity. Through theoretical derivation, flexoelectricity can be improved by designing the macroscopic symmetry of the material parameter distribution (including the piezoelectric coefficients) and device structure. As a demonstration, typical piezoelectric bimorph cantilevers (PBCs; Ag/PZT-5H/Ag/PZT-5H/Ag) are constructed with the two PZT-5H layers arranged in "head-to-tail" polarization (mirror symmetry) and "tail-to-tail" polarization (centrosymmetry), to design the macroscopic symmetry and thus to tune the flexoelectricity. The theoretical predictions and experimental results show that the tail-to-tail PBC achieves a flexoelectric coefficient (1.47 × 10 nC m), 20 times higher than that of the head-to-tail PBC (7 × 10 nC m) and conventional piezoelectric cantilevers (Ag/PZT-5H/Ag). Furthermore, by introducing spaced-interdigitated electrodes, the macroscopic symmetry of the head-to-tail PBC can be transformed from mirror to centrosymmetry, yielding a giant flexoelectric coefficient of 2.53 × 10 nC m. This strategy offers a dimension beyond traditional approaches for understanding and enhancing flexoelectricity, paving the way for its practical application.
所有材料中的对称性都会产生挠曲电效应。然而，挠曲电材料的应用受到大块材料中通常较低的电荷密度的限制。在本研究中，提出了一种涉及宏观对称性设计的通用策略来增强挠曲电效应。通过理论推导，挠曲电效应可以通过设计材料参数分布（包括压电系数）和器件结构的宏观对称性来提高。作为示例，构建了典型的压电双压电层悬臂梁（PBCs；Ag/PZT-5H/Ag/PZT-5H/Ag），其中两个PZT-5H层以“头对头”极化（镜面对称）和“尾对尾”极化（中心对称）排列，以设计宏观对称性从而调节挠曲电效应。理论预测和实验结果表明，尾对尾的PBC实现了挠曲电系数（1.47×10纳库仑·米），比头对头的PBC（7×10纳库仑·米）和传统压电悬臂梁（Ag/PZT-5H/Ag）高20倍。此外，通过引入间隔叉指电极，头对头PBC的宏观对称性可以从镜面转变为中心对称，产生2.53×10纳库仑·米的巨大挠曲电系数。该策略为理解和增强挠曲电效应提供了超越传统方法的维度，为其实际应用铺平了道路。
