Influence of antiphase boundaries on critical current densities in Yba2Cu3O7−ysingle crystals

2001 ◽  
Vol 16 (7) ◽  
pp. 1935-1941 ◽  
Author(s):  
Junko Shibata ◽  
Akihiro Oka ◽  
Teruo Izumi ◽  
Yuh Shiohara ◽  
Tsukasa Hirayama ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Critical Current ◽  
High Magnetic Field ◽  
Peak Effect ◽  
Antiphase Boundaries ◽  
Transmission Electron ◽  
Current Densities

Twinned and detwinned Yba2Cu3O7−y (Y123) single crystals were observed by transmission electron microscopy to investigate the influences of the lattice defects on the peak effect for Y123 single crystals. Twin boundaries with the spacing of 0.2–0.5 μm were seen only in the twinned Y123 single crystals. Antiphase boundaries (APBs) along the (110)Y123 plane were observed in both twinned and 0.5h-detwinned samples, which showed the peak effect in high magnetic field over 3 T at 70 K. In contrast, APBs were not found in 100h-detwinned sample. Critical current densities of this sample were small all over the range of the applied magnetic field. In conclusion, we suggest that APBs have a significant influence on the peak effect of Y123 single crystals in the high magnetic field.

Semi-Coherent Yttria Inclusions Occurring Spontaneously in YBa2Cu3O6+× Films Grown by Dc Magnetron Sputtering

1992 ◽  
Vol 275 ◽  
Author(s):  
T. I. Selinder ◽  
Z. Han ◽  
U. Helmersson ◽  
J. Magnusson ◽  
P. Norling ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Magnetron Sputtering ◽  
Critical Current ◽  
Film Growth ◽  
Number Density ◽  
Dc Magnetron Sputtering ◽  
High Quality ◽  
Transmission Electron ◽  
Current Densities

ABSTRACTSemi-coherent Y2O3 (yttria) inclusions have been observed in high quality, c-axis oriented YBa2Cu3O6+×,(YBCO) Alms. The inclusions were studied by transmission electron microscopy (TEM), and were found to be embedded in the YBCO matrix without disturbing its structure seriously. Their number density is estimated to higher than 2 × 1016 cm−3 in epitaxial YBCO films, having transport critical current densities in excess of 1 × 106 A cm−2 at 77 K. Magnetization measurements indicate a possible correlation between a high density of yttria inclusions and high pinning strength. The effects of the inclusions on film growth and microstructure is discussed.

Low-Tc phase formation at the grain boundaries and electromagnetic granularity in (Bi,Pb)2Sr2Ca2Cu3Ox silver-sheathed tapes

1993 ◽  
Vol 51 ◽  
pp. 940-941
Author(s):  
Yi Feng ◽  
A. Umezawa ◽  
H. S. Edelman ◽  
D. C. Larbalestier
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundaries ◽  
Critical Current ◽  
Ac Susceptibility ◽  
Transmission Electron ◽  
Heat Treated ◽  
Standard Powder ◽  
Current Densities ◽  
Powder In Tube

High resolution transmission electron microscopy (HRTEM) was performed on progressively heat treated Ag-clad (Bi,Pb)2Sr2Ca2Cu3Ox (2223) tapes and was correlated with their transport critical current densities, DC magnetization and AC susceptibility. HRTEM reveals the presence of a small number of half layers of the low Tc Bi2Sr2CaCu2Ox (2212) phase clustered at the numerous (001) twist grain boundaries. This residual 2212 phase produces electromagnetic granularity in a temperature range around 77K and thus directly controls the critical current.The Bi(Pb)-Sr-Ca-Cu-0 (BSCCO) Ag-clad tapes with the stoichiometric 2:2:2:3 starting composition were prepared by a standard powder-in-tube method. Sample A was heat treated at 817°C for 5 hours only. Sample B was first heat treated at 817°C for 24 hours, and then heat treated for 100 hours at the same temperature after two intermediate pressings. Sample C was heat treated at 830°C for 72 hours, and then heat treated for additional 196 hours after one intermediate pressing.

Transmission Electron Microscopy of Pb-doped Bi2Sr2Ca2Cu30x /Ag composite conductors prepared by the two-powder process: The effect of lead addition on critical current and microstructure

1994 ◽  
Vol 52 ◽  
pp. 798-799
Author(s):  
J. S. Luo ◽  
S. E. Dorris ◽  
M. T. Lanagan ◽  
V. A. Maroni
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Critical Current ◽  
Phase Evolution ◽  
Specific Method ◽  
X Ray ◽  
Transmission Electron ◽  
Composite Conductors ◽  
Current Densities ◽  
Lead Addition

Recent studies indicate that a more uniform and more fully reacted Pb-doped Bi2Sr2Ca2Cu3Ox (Bi-2223)phase can be reproducibly obtained within silver sheaths using a two-powder precursor in which the formation of Bi-2223 primarily involves reaction between lead-doped Bi2Sr2CaCu2Oz (Bi-2212) and other non-superconducting phases. In particular, the specific method of introducing lead was reported to significantly influence the phase evolution and superconducting properties of Bi-2223/Ag composite conductors.2 Composites made from lead-doped Bi-2212, where lead is fully incorporated into the Bi-2212 phase prior to its conversion to Bi-2223, exhibit sharper transition temperatures and higher critical current densities than those where lead is added in the form of non-superconducting PbO or Ca2PbO4 phases (Fig. I).2 In this paper, we present a combined investigation by transmission electron microscopy(TEM) and energy dispersive x-ray spectroscopy (EDX) of the composition and microstructure of the (Bi-2223)/Ag composite conductors. The observed differences are discussed with respect to the measured electrical properties.

Transmission Electron Microscopy study of Bi-based superconducting phases

1990 ◽  
Vol 48 (4) ◽  
pp. 50-51
Author(s):  
J.G. Wen ◽  
K.K. Fung
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Space Groups ◽  
Superconducting Phases ◽  
Ceramic Samples ◽  
Transmission Electron ◽  
Modulated Structures

Bi-based superconducting phases have been found to be members of a structural series represented by Bi2Sr2Can−1Cun−1On+4, n=1,2,3, and are referred to as 2201, 2212, 2223 phases. All these phases are incommensurate modulated structures. The super space groups are P2/b, NBbmb 2201, 2212 phases respectively. Pb-doped ceramic samples and single crystals and Y-doped single crystals have been studied by transmission electron microscopy.Modulated structures of all Bi-based superconducting phases are in b-c plane, therefore, it is the best way to determine modulated structure and c parameter in diffraction pattern. FIG. 1,2,3 show diffraction patterns of three kinds of modulations in Pb-doped ceramic samples. Energy dispersive X-ray analysis (EDAX) confirms the presence of Pb in the three modulated structures. Parameters c are 3 0.06, 38.29, 30.24Å, ie 2212, 2223, 2212 phases for FIG. 1,2,3 respectively. Their average space groups are all Bbmb.

scholarly journals Identification of Faults in Asbestos Minerals and Application to Pollution Studies

1976 ◽  
Vol 34 ◽  
pp. 616-617
Author(s):  
K. Seshan ◽  
H.-R. Wenk
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Twin Plane ◽  
Fibre Axis ◽  
Fibre Structure ◽  
Asbestos Fibre ◽  
Fibre Texture ◽  
Transmission Electron ◽  
Diffraction Patterns

Asbestos fibre texture occurs in various mineral groups (e.g. chrysotile, crocidolite, tremolite, grunerite, tourmaline) and it has been established that at least chrysotile is carcinogenic. We are investigating various aspects of the asbestos structure, with transmission electron microscopy (TEM) (1) in order to develop methods for unequivocal asbestos identification using minute samples and also to determine defects responsible for the fibre structure in these minerals which often occur as large, we 11-developed single crystals.In order to do this, we have started by investigating clinoamphibole asbestos such as tremolite Ca2Mg5[Si8O22] (OH, F)2 and crocidolite Na2 (Mg, Al, Fe3+, Fe2+) (Si8O22) (OH, F )2 , from California localities. In crocidoli te - asbestos we observed a high density of very narrow microtwins parallel to the fibre axis [001] (Fig. 1). They are often only 50-100Å wide. Diffraction patterns display the typical twin arrangement of spots and although preliminary contrast experiments are not yet conclusive the twin plane appears to be (100).

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