中国物理B ›› 2025, Vol. 34 ›› Issue (7): 76102-076102.doi: 10.1088/1674-1056/adda0a
Atomic insights into topochemical fluorination and strong octahedral tilt in La2CoO4
Yuzhou He(何玉洲)1,2,†, Ting Lin(林挺)3,†, Shiyu Wang(王诗雨)2, Ang Gao(高昂)2,4, Ziang Meng(孟子昂)5, Tianping Ying(应天平)2, Zhiqi Liu(刘知琪)5, Lin Gu(谷林)3, Qinghua Zhang(张庆华)2,‡, and Binghui Ge(葛炳辉)1,§
- 1 Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China;
2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
3 Beijing National Center for Electron Microscopy and Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China;
4 Institute of Environmental and Applied Chemistry, College of Chemistry, Central China Normal University, Wuhan 430079, China;
5 School of Materials Science and Engineering, Beihang University, Beijing 100191, China
Atomic insights into topochemical fluorination and strong octahedral tilt in La2CoO4
Yuzhou He(何玉洲)1,2,†, Ting Lin(林挺)3,†, Shiyu Wang(王诗雨)2, Ang Gao(高昂)2,4, Ziang Meng(孟子昂)5, Tianping Ying(应天平)2, Zhiqi Liu(刘知琪)5, Lin Gu(谷林)3, Qinghua Zhang(张庆华)2,‡, and Binghui Ge(葛炳辉)1,§
- 1 Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China;
2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
3 Beijing National Center for Electron Microscopy and Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China;
4 Institute of Environmental and Applied Chemistry, College of Chemistry, Central China Normal University, Wuhan 430079, China;
5 School of Materials Science and Engineering, Beihang University, Beijing 100191, China
摘要： Topochemical fluorination introduces significant structural distortions and emerging properties in perovskite oxides via substituting oxygen with fluorine. However, the rapid fluorination process and the similarity between F and O render the O/F site occupation and local lattice evolution during fluorination unclear. Here we investigated the atomic-scale O/F exchange in La$_{2}$CoO$_{4}$ and quantified the lattice distortion of three ordered structures: La$_{2}$CoO$_{3.5}$F, La$_{2}$CoO$_{3}$F$_{2}$, and La$_{2}$CoO$_{2.5}$F$_{3}$ by utilizing aberration-corrected electron microscopy. Atomic-resolved elemental mapping provides direct evidence for the O/F occupancy in interstitial and apical sites. We revealed that apical F ions induce significant octahedral tilting from 178$^\circ$ to 165$^\circ$, linearly proportional to the occupancy rate; and cause the obvious change in the fine structure O $K$ edge, meanwhile apical O is exchanged into interstitial sites. The strong octahedral tilt leads to the in-plane elongation of the [CoO$_{4}$F$_{2}$] octahedra. These findings elucidate the atomic-scale mechanisms of the entire fluorination process and highlight the significant role of F in tuning the octahedral tilt of functional oxides.
中图分类号: (Theory of crystal structure, crystal symmetry; calculations and modeling)
- 61.50.Ah