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<p>This study demonstrates the use of oxygen vacancy-induced planar defects to significantly enhance electrical polarization through a local flexoelectric effect. By introducing an appropriate level of aliovalent dopants, numerous local planar defects are induced in (Bi<sub>0.5</sub>, Na<sub>0.5</sub>)TiO<sub>3</sub>-based thin films. These defects, identified as oxygen-deficient structures through direct visualization of oxygen atoms and oxygen vacancies using integrated differential phase-contrast microscopy, result in the formation of head-to-head domain structures. Geometric phase analysis confirms that these structures exhibit a substantial local strain gradient of up to 10<sup>9 </sup>m<sup>-1</sup>, contributing significantly to the flexoelectric polarization. Consequently, a giant maximum polarization (<b>P</b><sub>m</sub>) of 161 μC cm<sup>-2</sup> under 750 kV cm<sup>-1</sup> and a remanent polarization <b>P</b><sub>r</sub> = 115 μC cm<sup>-2</sup> along with a coercive field of 250 kV cm<sup>-1</sup> are achieved, allowing these (Bi<sub>0.5</sub>, Na<sub>0.5</sub>)TiO<sub>3</sub>-based thin films to be used in low-power electronic applications. Crucially, the <b>P</b><sub>m</sub> and <b>P</b><sub>r</sub> of the thin films can be sustained at 133 and 98 μC cm<sup>-2</sup>, respectively, at 230 °C. Additionally, they exhibit exceptional high-temperature fatigue endurance, with <b>P</b><sub>m</sub> and <b>P</b><sub>r</sub> demonstrating a negligible reduction of less than 9% after 10<sup>7</sup> cycles under 750 kV cm<sup>-1</sup> at 230 °C. These values surpass those previously reported for oxide perovskite thin films at elevated temperatures, demonstrating potential applications of our thin films in high-temperature environments. Our findings offer promising avenues for advancing the application fields of ferroelectric thin films.</p>

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Flexoelectricity-driven giant polarization in (Bi, Na)TiO3-based ferroelectric thin films

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月26日

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  • Yunlong Sun,
  • Ranming Niu,
  • Zizheng Song,
  • Shiyu Tang,
  • Huizhong Wang,
  • Xun Geng,
  • Ji Zhang,
  • Jack Yang,
  • Claudio Cazorla,
  • Changqing Guo,
  • Shery L. Y. Chang,
  • Xiaojie Lou,
  • Houbing Huang,
  • Zibin Chen,
  • Shujun Zhang,
  • Danyang Wang

摘要

This study demonstrates the use of oxygen vacancy-induced planar defects to significantly enhance electrical polarization through a local flexoelectric effect. By introducing an appropriate level of aliovalent dopants, numerous local planar defects are induced in (Bi0.5, Na0.5)TiO3-based thin films. These defects, identified as oxygen-deficient structures through direct visualization of oxygen atoms and oxygen vacancies using integrated differential phase-contrast microscopy, result in the formation of head-to-head domain structures. Geometric phase analysis confirms that these structures exhibit a substantial local strain gradient of up to 109 m-1, contributing significantly to the flexoelectric polarization. Consequently, a giant maximum polarization (Pm) of 161 μC cm-2 under 750 kV cm-1 and a remanent polarization Pr = 115 μC cm-2 along with a coercive field of 250 kV cm-1 are achieved, allowing these (Bi0.5, Na0.5)TiO3-based thin films to be used in low-power electronic applications. Crucially, the Pm and Pr of the thin films can be sustained at 133 and 98 μC cm-2, respectively, at 230 °C. Additionally, they exhibit exceptional high-temperature fatigue endurance, with Pm and Pr demonstrating a negligible reduction of less than 9% after 107 cycles under 750 kV cm-1 at 230 °C. These values surpass those previously reported for oxide perovskite thin films at elevated temperatures, demonstrating potential applications of our thin films in high-temperature environments. Our findings offer promising avenues for advancing the application fields of ferroelectric thin films.