Giant Flexoelectric Polarization in a Micromachined Ferroelectric Diaphragm

Authors

  • Zhihong Wang,

    Corresponding author
    1. Advanced Nanofabrication Core Lab, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
    • Advanced Nanofabrication Core Lab, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
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  • Xi Xiang Zhang,

    1. Advanced Nanofabrication Core Lab, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
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  • Xianbin Wang,

    1. Advanced Nanofabrication Core Lab, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
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  • Weisheng Yue,

    1. Advanced Nanofabrication Core Lab, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
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  • Jingqi Li,

    1. Advanced Nanofabrication Core Lab, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
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  • Jianmin Miao,

    1. School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798
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  • Weiguang Zhu

    Corresponding author
    1. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798
    • School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798.
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Abstract

The coupling between dielectric polarization and strain gradient, known as flexoelectricity, becomes significantly large on the micro- and nanoscale. Here, it is shown that giant flexoelectric polarization can reverse remnant ferroelectric polarization in a bent Pb(Zr0.52Ti0.48)O3 (PZT) diaphragm fabricated by micromachining. The polarization induced by the strain gradient and the switching behaviors of the polarization in response to an external electric field are investigated by observing the electromechanical coupling of the diaphragm. The method allows determination of the absolute zero polarization state in a PZT film, which is impossible using other existing methods. Based on the observation of the absolute zero polarization state and the assumption that bending of the diaphragm is the only source of the self-polarization, the upper bound of flexoelectric coefficient of PZT film is calculated to be as large as 2.0 × 10−4 C m−1. The strain gradient induced by bending the diaphragm is measured to be on the order of 102 m−1, three orders of magnitude larger than that obtained in the bulk material. Because of this large strain gradient, the estimated giant flexoelectric polarization in the bent diaphragm is on the same order of magnitude as the normal remnant ferroelectric polarization of PZT film.

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