Electron Crystallographic Study

of

Bi-based Superconductors

using

Multi-dimensional Direct Methods

Electron Crystallographic Study

of

Bi-based Superconductors

using

Multi-dimensional Direct Methods

Why Electrons ?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

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

Scattering of X-rays and Electronsby Different Elements

Scattering of X-rays and Electronsby Different Elements

Relative scattering power

Relative scattering power

OO OO

Sin/Sin/

BiBi

SrSr

CaCaCuCu

X-raysX-rays

ElectronsElectrons

Bismuthbi-layer

Perovskitelayer

Bismuthbi-layer

Bi-based SuperconductorsBi-based Superconductors

n = 1 n = 2 n = 3Bi2201 Bi2212 Bi2223

Bi-OBi-O

Sr-OCu-OSr-O

Sr-OCu-OCa-OCu-OSr-O

Sr-OCu-OCa-OCu-OCa-OCu-OSr-O

Bi-OBi-O

Bi-OBi-O

Bi-OBi-O Bi-O

Bi-O Bi-OBi-O

c

Bi2Sr2Can1CunO2n+4+xBi2Sr2Can1CunO2n+4+x

Electron diffraction analysis ofthe Bi-2223 superconductor

Electron diffraction analysis ofthe Bi-2223 superconductor

Space group: P [Bbmb] 1 -1 1a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b*

*The average structure is known*

Bi-2223 [100] projected potentialBi-2223 [100] projected potentialSpace group: P [Bbmb] 1 -1 1a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b*Space group: P [Bbmb] 1 -1 1a = 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

a3

a4

Bi-2223Bi-2223

cut at a2 = 0 and projected down the a1 axis

cut at a2 = 0 and projected down the a1 axis

Space group: P [Bbmb] 1 -1 1a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b*

a1 = a, a2 = b 0.117d,a3 = c, a4 = d

4-dimensional metal atoms4-dimensional metal atoms

Image Processing of Bi-2212Image Processing of Bi-2212Space 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

FTFT

FT-1FT-1Phase extension

Phase extension

Image Processing of Bi-2212 (continued)Image Processing of Bi-2212 (continued)

BiBiSrSr

CuCuCaCa

CuCuSrSrBiBi

bb

cc

22

8844

11

Oxygenin Cu-O layerOxygenin Cu-O layer

Original image

Enhanced image

b

c

O atoms on the Cu-O layer

O atoms on the Cu-O layer

Bi-OBi-OSr-OSr-O

Sr-OSr-OBi-OBi-O

Cu-OCu-O

O (extra)O (extra)

Electron diffraction analysis of Bi-2201Electron diffraction analysis of Bi-2201

RT = 0.32 Rm = 0.29 RS1 = 0.29 RS2 = 0.36 RS3 = 0.52

RT = 0.32 Rm = 0.29 RS1 = 0.29 RS2 = 0.36 RS3 = 0.52

Space group: P[B 2/b] -1]; a = 5.41, b = 5.43, c = 24.6Å,= 90o; q = 0.217b* + 0.62c*Space group: P[B 2/b] -1]; a = 5.41, b = 5.43, c = 24.6Å,= 90o; q = 0.217b* + 0.62c*

Bi-2201Bi-2201

Influence of Influence of thermal thermal

motion motion ((BB)) and and

Modulation Modulation ((MM)) to the to the dynamical dynamical diffractiondiffraction

Bi-2201Bi-2201

Influence of Influence of thermal thermal

motion motion ((BB)) and and

Modulation Modulation ((MM)) to the to the dynamical dynamical diffractiondiffraction

Experimental B and M

B set to zero

M set to zero B,M set to zero

Sample thickness: ~5Å Bi-2201Bi-2201

The effect of sample

thickness

Bi-O

Bi-O

Sr-O

Sr-OCu-O

~100Å~200Å~300Å

Extra oxygenOxygen inCu-O layer