scholarly journals Observation of bound surface states in grain-boundary junctions of high-temperature superconductors

1998 ◽  
Vol 58 (17) ◽  
pp. 11197-11200 ◽  
Author(s):  
L. Alff ◽  
A. Beck ◽  
R. Gross ◽  
A. Marx ◽  
S. Kleefisch ◽  
...  
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
High Temperature Superconductors ◽  
Surface States

Site Exchange in High Temperature Superconductors

1987 ◽  
Vol 99 ◽  
Author(s):  
D. J. Li ◽  
H. Shibahara ◽  
J. P. Zhang ◽  
L. D. Marks
Keyword(s):  
Heavy Metals ◽  
High Temperature ◽  
Grain Boundary ◽  
High Temperature Superconductors ◽  
Planar Defects ◽  
Electron Microscopical Analysis ◽  
Site Exchange ◽  
Copper Sites ◽  
Electron Microscopical ◽  
Brown Powder

ABSTRACTElectron microscopical analysis of brown powders of composition YBa2Cu3O6.5 produced by oil quenching and conventionally produced orthorhombic GdBa2Cu3O7-δ show in both cases clear evidence for site exchange both between the different heavy metals and the heavy metals and the copper sites. For instance, the brown powder is a mixture of phases which are based upon two trigonal phases, both with a=0.536 and c=0.666 nm, one with the Y atoms stacked on the (111) planes of the parent perovskite structure and the second where the Y atoms of this structure have interchanged with one of the copper sites. The GdBa2Cu3O7-δ, material shows numerous planar defects on (001) planes which can be understood as copper rich regions with additional copper planes in the Ba or Gd sites. These results, together with earlier reports of order-disorder in YBa2Cu3O7-δ, strongly indicate that there exist ordering energies in these materials which may be important with respect to the current indications of the important of grain boundary phases in degrading the performance of some superconductors.

Non-Stoichiometry at Dislocation Cores in Perovskites and Related Materials

2001 ◽  
Vol 7 (S2) ◽  
pp. 306-307
Author(s):  
Gerd Duscher ◽  
M. Kim ◽  
N.D. Browning ◽  
D. K. Christen ◽  
C. Cantoni ◽  
...  
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
High Temperature Superconductors ◽  
Small Sample ◽  
Structural Units ◽  
Band Bending ◽  
Single Grain ◽  
Z Contrast ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Z-contrast images and electron energy loss spectra (EELS) were obtained from low angle grain boundaries in SrTiO3 and YBa2Cu3O7-x (YBCO). Z-contrast images are easy to interpret and especially useful for positioning the beam to acquire EELS data from small sample areas [1], because both these techniques can be performed simultaneously.In high-temperature superconductors even a single grain boundary can reduce the critical current by up to four orders of magnitude. The band-bending model can quantitatively explain this phenomenon. YBCO is a hole-doped superconductor with about one hole per unit cell for optimum doping at x close to zero. It has a structure closely related to the perovskite structure, and Z-contrast images have shown that the dislocation cores are made up of similar structural units as in SrTiO3.[2,3] Our EELS measurements show clear evidence for band bending effects around isolated dislocation cores in an undoped 8° low angle grain boundary.

Current transport of the [001]-tilt low-angle grain boundary in high temperature superconductors

2013 ◽  
Vol 103 (23) ◽  
pp. 232602 ◽  
Author(s):  
Donghua Yue ◽  
Xingyi Zhang ◽  
Jun Zhou ◽  
Youhe Zhou
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
High Temperature Superconductors ◽  
Current Transport

scholarly journals JOSEPHSON (001) TILT GRAIN BOUNDARY JUNCTIONS OF HIGH-TEMPERATURE SUPERCONDUCTORS

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3194-3198
Author(s):  
RICHARD A. KLEMM ◽  
GERALD B. ARNOLD
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Fermi Surface ◽  
Critical Current ◽  
High Temperatures ◽  
High Temperature Superconductors ◽  
Surface Topology ◽  
Phase Sensitive ◽  
Fermi Surface Topology ◽  
Tilt Grain Boundary

We calculate the Josephson critical current Ic across in-plane (001) tilt grain boundary junctions of high-temperature superconductors. We assume the Fermi surface has either an electron-doped form, or one of three hole-doped forms, and either random or specular tunneling across the junctions. We find that in-plane 'phase-sensitive' experiments are consistent with our results for the electron-doped superconductors. For the hole-doped superconductors, however, the results depend strongly upon the details of both the Fermi surface topology and the nature of the tunneling, and are therefore considerably less robust than has generally been believed. Hence, the tricrystal, tetracrystal, and interferometry experiments on hole-doped high-temperatures superconductors are unreliable, and should be redesigned.

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