Grain Boundary Structure and Properties of High-Tc Superconductors

1992 ◽  
Vol 275 ◽  
Author(s):  
K. Jagannadham ◽  
J. Narayan
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Boundary Effects ◽  
Boundary Structure ◽  
Excess Charge ◽  
High Tc Superconductors ◽  
High Tc ◽  
Grain Boundary Structure

ABSTRACTWe have modelled the grain boundaries in high-Tc superconducting oxides and determined the critical current density. The tunneling of superconducting pairs across the coalesced regions is used to determine the boundary effects. The length of the coalesced regions, with continuity of the Cu-O planes maintained by relaxation of the atom positions, is determined by minimization of the energy of the configuration. The depression of the order parameter is evaluated using the continuity conditions at the boundary in the proximity effect formulation. The excess charge distribution at the core of the boundary, determined from the solution to the Poisson's equation, is used to determine the scattering of the superconducting pairs. The width of the boundary, evaluated from modelling, determines the transmission coefficient for tunnelingof superconducting pairs. The critical current density is expressed in terms of these four important factors associated with the grain boundary. All the experimental results are explained by the present modelling of the grain boundary effects.

Grain Boundary Modelling and Correlation with Critical Current Densities in High‐Tc Superconductors

1989 ◽  
Vol 169 ◽  
Author(s):  
K. Jagannadham ◽  
J. Narayan
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Weak Coupling ◽  
Weak Coupling Limit ◽  
Excess Charge ◽  
High Tc Superconductors ◽  
High Tc ◽  
Geometrical Modelling ◽  
Current Densities

AbstractGeometrical modelling of grain boundaries in 123‐YBaCuO and 2223‐TlBaCaCuO systems is carried out for several misorientat‐ions. The a‐b and the a‐c type coincidence boundaries are analyzed to determine the fraction of Cu‐O planes that are continuous and the excess charge present at the boundary voids. The interg‐rain critical current density is determined as a function of the misorientation and the width of the boundary. The tunneling of superconductor pairs through the regions of distortions, giving rise to depression of the order parameter at the boundaries,is used to determine the critical current density in the weak coupling limit.

INFLUENCE OF GRAIN BOUNDARIES ON THE TRANSPORT CRITICAL CURRENT DENSITY OF HIGH Tc SUPERCONDUCTORS

1991 ◽  
Vol 05 (14n15) ◽  
pp. 993-999 ◽  
Author(s):  
HUIMIN SHAO ◽  
MU LU ◽  
TIANCHANG LU ◽  
XICHUN JIN ◽  
LINJIANG SHEN ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Grain Boundaries ◽  
Critical Current ◽  
Current Density ◽  
Transport Critical Current Density ◽  
High Tc Superconductors ◽  
High Tc ◽  
Preparation Conditions ◽  
Percolation Path ◽  
Superconducting Current

This paper describes our efforts to improve the preparation conditions of YBCO samples and increase their density by doping with Sn, F, or Ag and our analysis of the influence of different grain boundaries on superconducting current. We come to the conclusion that, as the grain boundaries have an insulation layer between them forming Josephson junctions and the metalled grain boundaries form proximity junctions which are kind of weak couplings for superconductors, the current-carrying capacity of samples having such grain boundaries cannot be expected to greatly increase. Only by increasing the density of samples and purifying the grain boundaries can a better percolation path for supercurrent be created, thereby considerably increasing the critical current density.

scholarly journals Dependence of critical current density on microstructure and processing of high-Tc superconductors

1994 ◽  
Vol 23 (11) ◽  
pp. 1191-1197 ◽  
Author(s):  
A. Goyal ◽  
E. D. Specht ◽  
Z. L. Wang ◽  
D. M. Kroeger ◽  
J. A. Sutliff ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
High Tc Superconductors ◽  
High Tc

TEM Characterization of Grain Boundary Structure in YBCO Coated Conductors

2000 ◽  
Vol 6 (S2) ◽  
pp. 394-395
Author(s):  
H. Kung ◽  
J.P. Hirth ◽  
S.R. Foltyn ◽  
P.N. Arendt ◽  
Q.X. Jia ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Grain Boundaries ◽  
Critical Current ◽  
Current Density ◽  
Lattice Mismatch ◽  
Coupling Effect ◽  
High Temperature Superconductors ◽  
Coated Conductors ◽  
Boundary Structure

Studies of defects, such as grain boundaries, in high temperature superconductors (HTS) are important due to the interaction of the defects with flux-bearing vortices. The benefit of in-plane grain alignment has been documented in YBCO thin film bicrystals, in which the high critical current density (Jc) observed across small angle grain boundaries deteriorates exponentially with grain boundary angles beyond ∼ 7°. In addition to the weak coupling effect, a grain boundary may also influence the transport properties via the grain boundary dislocations (GBDs) serving as pinning centers to increase the critical current density. There have been a number of studies on grain boundary structures in YBCO. Despite many differences in structure among the different types of boundaries, it has been established that the low angle [001] tilt boundary in YBCO consists of aperiodic array of edge type GBDs with [100] type Burgers vector that accommodate the lattice mismatch, and the regions between the GBDs are channels of relatively undisturbed lattices [1].

Sign in / Sign up

Export Citation Format

Share Document