Dynamics of Anisotropic Oxygen-Ion Migration in Strained Cobaltites
Qinghua Zhang, Fanqi Meng, Ang Gao, Xinyan Li, Qiao Jin, Shan Lin, Shengru Chen, Tongtong Shang, Xing Zhang, Haizhong Guo, Can Wang, Kuijuan Jin, Xuefeng Wang, Dong Su, Lin Gu, Er‐Jia Guo
Abstract
Orientation control of the oxygen vacancy channel (OVC) is highly desirable for tailoring oxygen diffusion as it serves as a fast transport channel in ion conductors, which is widely exploited in solid-state fuel cells, catalysts, and ion-batteries. Direct observation of oxygen-ion hopping toward preferential vacant sites is a key to clarifying migration pathways. Here we report anisotropic oxygen-ion migration mediated by strain in ultrathin cobaltites via in situ thermal activation in atomic-resolved transmission electron microscopy. Oxygen migration pathways are constructed on the basis of the atomic structure during the OVC switching, which is manifested as the vertical-to-horizontal OVC switching under tensile strain but the horizontal-to-diagonal switching under compression. We evaluate the topotactic structural changes to the OVC, determine the crucial role of the tolerance factor for OVC stability, and establish the strain-dependent phase diagram. Our work provides a practical guide for engineering OVC orientation that is applicable to ionic-oxide electronics.