Observation of Oxygen Vacancies in Perovskite Oxide by a 200kV HREM

通过 200kV HREM 观察钙钛矿氧化物中的氧空位

• 批准号: 06805002
• 负责人: SHIBAHARA Hiroyasu
• 金额: $ 1.09万
• 依托单位: KYOTO UNIVERSITY OF EDUCATION
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06805002/
• 关键词: HREM; Oxygen-vacancies; Perovskite; IMAGE PROCESSING; DEFECTIVE-STRUCTURE; ペロブスカイト; LaMnO3; イメージングプレート

The perovskites with the general formula XYO_3 have been extensively studied because of their interesting ferroelectric ad magnetic properties. The systems of LaMnO_<3-X> and BaMnO_<3-X> consist of a staking of close-packed layrs of LaO_3/BaO_3 with Mn metals occupying interlayr octahedral site. Analyzes of their oxygen-defective structures are of interest because of the magnetic properties depending on the content of oxygen vacancy. Establishment of imaging condition of a HREM for reflecting oxygen-defective structure is of importance. The structural determination and quantification of oxygen vacancies in LaMnO_<3-X> were carried out in 200/300kV HREM equipped with an imaging plate. On the basis of direct observation with HREM and the aid of computer simulation and image processing, optimum imaging conditions were found, where oxygen atoms and the vacancies are imaged as bright spots in a "dark-spot image". Under the optimum imaging conditions, the dependence of image contrast on the atomic occupancies of the oxygen sites and the thickness of the samples was discussed on the basis of dynamical diffraction theory. By an imaging plate, the atomic occupancies were quantitatively estimated from the intensity distributions of the bright spots in the observed image contrast. Using the relaxd structure derived from molecular dynamics simulation, image contrast based on the multi-slice method could assist the understanding of the observed image contrast by HREM.Besides, as an application of structural determination by the present method, hydroxyapatite in tooth crystals was studied to ascertain the positions of the OH^- groups.

通式为XYO_3的钙钛矿材料由于其独特的铁电和磁性而得到了广泛的研究。LaMnO_3<3-X>和BaMnO_3<3-X>体系由LaO_3/BaO_3密排层堆叠而成，Mn金属占据层间八面体位置。分析其氧缺陷结构的兴趣，因为磁性能取决于氧空位的含量。建立反映氧缺陷结构的高分辨电镜成像条件是重要的。在<3-X>200/300 kV高分辨电子显微镜上，用成象板对LaMnO_2进行了结构测定和氧空位定量。在高分辨电子显微镜直接观察的基础上，借助于计算机模拟和图像处理，找到了最佳成像条件，使氧原子和空位在“暗斑像”中成像为亮点。在最佳成像条件下，根据动态衍射理论，讨论了氧位原子占有率和样品厚度对像衬度的影响。通过成像板，从观察到的图像对比度中的亮点的强度分布定量地估计原子占位。利用分子动力学模拟得到的弛豫结构，基于多切片方法的图像对比度可以帮助理解高分辨电子显微镜观察到的图像对比度。此外，作为本方法结构确定的应用，对牙齿晶体中的羟基磷灰石进行了研究，以确定OH^-基团的位置。

项目成果

H. Shibahara: "OXYGEN-DEFECTIVE STRUCTURE IN PEROVSKITE BY HREM" Proc. of the 8th Chinese-Japanese Electron Microscopy Seminor. (印刷中). (1996)

H. Shibahara：“HREM 钙钛矿中的氧缺陷结构”，第八届中日电子显微镜研讨会论文集（1996 年出版）。

H. Shibahara: "Quantification of Oxygen Vacancies in Perovskite using a 300kV HREM with an Imaging Plate" J. Electron Microsc.44. 174-181 (1995)

H. Shibahara：“使用带有成像板的 300kV HREM 对钙钛矿中的氧空位进行定量”J. Electron Microsc.44。

H. Shibahara: "HREM Observation of Oxygen-Defective Structure in LaMnO_<3-x>" Electron Microscopy (Proc. of the 13th International Congress on Electron Microscopy). 2,B. 871-872 (1994)

H. Shibahara：“LaMnO_<3-x> 中氧缺陷结构的 HREM 观察”电子显微镜（第 13 届国际电子显微镜大会论文集）。

H. Shibahara: "HREM Study of Oxygen-Defective LaMnO_<3-x> with Twin Structure" J. Ceramics Society of Japan. 104. 11-16 (1996)

H. Shibahara：“具有孪生结构的氧缺陷 LaMnO_<3-x> 的 HREM 研究”J. 日本陶瓷学会。

H. Shibahara: "High Resolution Electron Microscopic Observation of Hydroxyapatite in Tooth Crystals" J. Electron Microsc.43. 89-94 (1994)

H. Shibahara：“牙齿晶体中羟基磷灰石的高分辨率电子显微镜观察”J. Electron Microsc.43。