Synthesis of One-dimensional Nano-sized Defects in High Tc Superconductor

Using the dedicate VG-HB5 STEM microscope, the crystal structure of high Tc superconductor of YBa2Cu3O7-x has been studied via high resolution STEM (HRSTEM) imaging and nanobeam (∽3A) diffraction patterns. Figure 1(a) and 2(a) illustrate the HRSTEM image taken at 10' times magnification along [001] direction and [100] direction, respectively. In figure 1(a), a grain boundary with strong field contrast is seen between two crystal regions A and B. The grain boundary appears to be parallel to a (110) plane, although it is not possible to determine [100] and [001] axes as it is in other regions which contain twin planes [3]. Following the horizontal lattice lines, from left to right across the grain boundary, a lattice bending of ∽4° is noticed. Three extra lattice planes, indicated by arrows, were found to terminate at the grain boundary and form dislocations. It is believed that due to different chemical composition, such structure defects occur during crystal growth. No bending is observed along the vertical lattice lines.

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Intergrowth of modulated structures in high Tc Bi-Sr-Ca-Cu-O superconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100173510 ◽

1990 ◽

Vol 48 (4) ◽

pp. 76-77

Author(s):

A.Q. He ◽

G.W. Qiao ◽

J. Zhu ◽

H.Q. Ye

Keyword(s):

Twin Structure ◽

Modulated Structure ◽

High Tc ◽

One Dimensional ◽

Lattice Constants ◽

Superconducting Phases ◽

Modulated Structures ◽

Layer Structures

Since the first discovery of high Tc Bi-Sr-Ca-Cu-O superconductor by Maeda et al, many EM works have been done on it. The results show that the superconducting phases have a type of ordered layer structures similar to that in Y-Ba-Cu-O system formulated in Bi2Sr2Can−1CunO2n+4 (n=1,2,3) (simply called 22(n-1) phase) with lattice constants of a=0.358, b=0.382nm but the length of c being different according to the different value of n in the formulate. Unlike the twin structure observed in the Y-Ba-Cu-O system, there is an incommensurate modulated structure in the superconducting phases of Bi system superconductors. Modulated wavelengths of both 1.3 and 2.7 nm have been observed in the 2212 phase. This communication mainly presents the intergrowth of these two kinds of one-dimensional modulated structures in 2212 phase.

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Electron-Probe Quantitative Energy-Dispersive Analysis of Trace Magnesium Concentrations in Ag-Mg Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010016501x ◽

1996 ◽

Vol 54 ◽

pp. 510-511

Author(s):

R. B. Marinenko

Keyword(s):

Electron Probe ◽

Energy Dispersive Spectrometry ◽

Mg Alloys ◽

Energy Dispersive ◽

Energy Dispersive Analysis ◽

High Tc ◽

Alloy Wire ◽

High Tc Superconductor ◽

Eds Analysis ◽

Superior Mechanical Properties

Internally oxidized Ag-Mg alloys are used as sheaths for high Tc superconductor wires because of their superior mechanical properties. The preparation and characteristics of these materials have been reported. Performance of the sheaths depends on the concentration of the magnesium which generally is less than 0.5 wt. percent. The purpose of this work was to determine whether electron probe microanalysis using energy dispersive spectrometry (EDS) could be used to quantitate three different Ag-Mg alloys. Quantitative EDS analysis can be difficult because the AgL escape peak occurs at the same energy (1.25 keV) as the Mg Kα peak. An EDS spectrum of a Ag-Mg alloy wire is compared to a pure Ag spectrum in Fig. 1.

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