Grant-in-Aid for Overseas Scientific Survey.
|Allocation Type||Single-year Grants |
|Research Institution||Institute for Materials Research, Tohoku University |
HIRAGA Kenji(1989) Professor Institute for Materials Research, Tohoku University, 金属材料研究所, 教授 (30005912)
平賀 賢二(1989) 東北大, 金属材料研究所, 教授
平林 真(1988) 東北大, 金属材料研究所, 教授
H. Sato パデュー大学, 材料工学科, 教授
大西 直乏 東北大学, 金属材料研究所, 日本学術振興会. 特別 (60201977)
進藤 大輔 東北大学, 金属材料研究所, 助手 (20154396)
小野塚 喬 東北大学, 金属材料研究所, 助手 (10005936)
HIRABAYASHI M. College of Science & Engineering, Iwaki - Meisei University, 理工学部, 教授 (00005836)
SHINDO D. Institute for Materials Research, Tohoku University
OHNISHI N. Fellow, Japan Society for the Promotion of Science
ONOZUKA T. Institute for Materials Research, Tohoku University
SATO H. School of Materials Engineering, Purdue University
|Project Period (FY)
1988 – 1989
Completed(Fiscal Year 1989)
|Budget Amount *help
¥4,000,000 (Direct Cost : ¥4,000,000)
Fiscal Year 1989 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1988 : ¥3,000,000 (Direct Cost : ¥3,000,000)
|Keywords||High-resolution electron microscopy / Superconducting oxide / Incommensurate modulated structue / Electron energy loss spectroscopy / Oxygen K-edge / Bi-Sr-Ca-Cu-O / Tl-Ba-Ca-Cu-O|
This work has originally started five years ago by the support of Japan-U.S. Science Cooperation Program under the auspices of JSPS and NSF on "Low temperature high-resolution electron microscopy of phase transition and solid state reactions". Under this program, the techniques of HRTEM at low temperature were explored for studying superconducing intermetallic compounds. Because the cooperative efforts have been done so effectively, this research program was initiated for development of high Tc oxide superconducters with the use of not only the low temperature technique but also analytical electron microscopy as well as atomic-scale electron microscopy at ambient temperature. Major results obtained in this work are summarized as follows.
1: Crystal structure of Bi_2Sr_2CaCu_2Ox has been studied by high resolution electron microscopy with particular attention to its incommensurate modulation. Based on detailed examination over wide areas, the incommensurate periodicity along the b-axis w
hich is 4.8 times of the basic unit b_o of the orthorhombic Bi_4Ti_3O_<12> type lattice can be interpreted well with a structure model consisting of two kinds of domain with the periods of 4.5 b_o and 5.0 b_o. The atomic arrangement in the incommensurate modulated structure is directly proposed from the high resolution observation.
2: Using a parallel detection system of electron energy loss spectroscopy (EELS), fine spectra near oxygen K- edge in superconducting Y-, Bi- and Tl-oxides have been measured. We found that a peak at about 530 eV indicates the presence of a hole state, and the peak intensity depends on the crystallographic orientation and the oxygen concentration. It is concluded that the hole concentration decreases with the increase of Tc, and the hole is associated with the 2p_<xy> orbit in the Cu-O plane.
3: High density, high Tc superconducting ceramic films have been prepared from precursor of melt-quench amorphous Bi-Sr-Ca-Cu-O system. Microstructure and its correlation with the high Tc superconductivity are clarified by high resolution electron microscopy. Detailed investigations combining with analytical electron microscopy using EDX and EELS are now in progress. Less