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Electron Crystallographic Study of Bi-based Superconductors using

Electron Crystallographic Study of Bi-based Superconductors using Multi-dimensional Direct Methods. Why Electrons ?. 1. Electrons are better for studying minute and imperfect crystalline samples 2. Electron microscopes are the only instrument that can produce

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Electron Crystallographic Study of Bi-based Superconductors using

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  1. Electron Crystallographic Study of Bi-based Superconductors using Multi-dimensional Direct Methods

  2. Why Electrons ? 1. Electrons are better for studying minute and imperfect crystalline samples 2. Electron microscopes are the only instrument that can produce simultaneously EM’s and ED’s for the same crystalline sample at atomic resolution 3. Electrons are better for revealing light atoms in the presence of heavy atoms

  3. Bi X-rays Electrons Sr Cu Ca Scattering of X-rays and Electrons by Different Elements Relative scattering power Sinq /l ~ 0.31 O O

  4. Bismuth bi-layer Perovskite layer Bismuth bi-layer Bi-based Superconductors Bi2Sr2Can-1CunO2n+4+x n = 1 n = 2 n = 3 Bi-2201 Bi-2212 Bi-2223 Bi-O Bi-O Bi-O Bi-O Bi-O Bi-O Sr-O Cu-O Ca-O Cu-O Ca-O Cu-O Sr-O c Sr-O Cu-O Ca-O Cu-O Sr-O Sr-O Cu-O Sr-O Bi-O Bi-O Bi-O Bi-O Bi-O Bi-O

  5. Electron diffraction analysis of the Bi-2223 superconductor Space group: P [Bbmb] 1 -1 1 a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b* *The average structure is known*

  6. Bi-2223 [100]projected potential Space group: P [Bbmb] 1 -1 1 a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b* RsymM = 0.12 (Nref. =42) RsymS = 0.13 (Nref. = 70) Rm = 0.16 Rs = 0.17

  7. a3 a4 Bi-2223 4-dimensional metal atoms cut at a2 = 0 and projected down the a1 axis Space group: P [Bbmb] 1 -1 1 a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b* a1 = a, a2 = b -0.117d, a3 = c, a4 = d

  8. FT FT-1 Image Processing of Bi-2212 Space group: N [Bbmb] 1 -1 1 a = 5.42, b = 5.44, c = 30.5Å; q = 0.22b* + c* EM image from Dr. S. Horiuchi Phase extension

  9. 2 Bi Sr Cu Ca Cu Sr Bi 1 8 Oxygen in Cu-O layer 4 Image Processing ofBi-2212(continued) Original image Enhanced image c b

  10. O atoms on the Cu-O layer Bi-O c Sr-O Cu-O Sr-O Bi-O b O (extra) Electron diffraction analysis of Bi-2201 Space group: P[B 2/b] -1]; a = 5.41, b = 5.43, c = 24.6Å, b = 90o; q = 0.217b* + 0.62c* RT = 0.32 Rm = 0.29 RS1 = 0.29 RS2 = 0.36 RS3 = 0.52

  11. Experimental B and M Bi-2201 Influence of thermal motion (B) and Modulation (M) to the dynamical diffraction B set to zero B,M set to zero M set to zero

  12. Sample thickness: ~5Å ~300Å ~100Å ~200Å Bi-O Sr-O Cu-O Sr-O Bi-O Oxygen in Cu-O layer Extra oxygen Bi-2201 The effect of sample thickness

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