Zhang Yang, Shi Xiaoming, Sung Suk Hyun, Li Cong, Huang Houbing, Yu Pu, El Baggari Ismail
The Rowland Institute at Harvard, Harvard University, Cambridge, MA 02138, USA.
Department of Physics, University of Science and Technology Beijing, Beijing, China.
Sci Adv. 2025 Sep 5;11(36):eadx9804. doi: 10.1126/sciadv.adx9804. Epub 2025 Sep 3.
Ferroelectricity in BaTiO was observed nearly 80 years ago, but the mechanism underlying its ferroelectric-paraelectric phase transition remains elusive. The order-disorder transition has been recognized as playing a critical role; however, the precise nature of the order parameter still remains under scrutiny, including the local dipole direction and the correlations above and below the Curie temperature. Using in situ scanning transmission electron microscopy, we directly map polar displacements in BaTiO across the ferroelectric-paraelectric phase transition, providing atomistic insights into an order-disorder mechanism. Atomic tracking reveals finite polar Ti displacements in the paraelectric phase where they manifest as random polar nanoregions. The displacements align along <111> direction in both the ferroelectric and paraelectric phases. The paraelectric-ferroelectric transition emerges from real-space correlations of the <111> polar Ti displacements. Our direct visualizations provide atomic insights into the order-disorder mechanism in the ferroelectric-paraelectric transition of BaTiO.
近80年前就观察到了钛酸钡中的铁电性，但其铁电-顺电相变的机制仍然难以捉摸。有序-无序转变被认为起着关键作用；然而，序参量的确切性质仍在研究之中，包括局部偶极子方向以及居里温度上下的相关性。利用原位扫描透射电子显微镜，我们直接绘制了钛酸钡在铁电-顺电相变过程中的极移图，为有序-无序机制提供了原子尺度的见解。原子追踪揭示了顺电相中有限的极性钛位移，它们表现为随机的极性纳米区域。在铁电相和顺电相中，位移都沿<111>方向排列。顺电-铁电转变源于<111>极性钛位移的实空间相关性。我们的直接可视化结果为钛酸钡铁电-顺电转变中的有序-无序机制提供了原子尺度的见解。
