M. Mosbah et al., A STUDY OF THE MICROSTRUCTURE AND THE CRITICAL CURRENT-DENSITY OF LA1.85SR0.15CUO4 SUPERCONDUCTOR, Physica. C, Superconductivity, 209(4), 1993, pp. 463-471
The irreversible magnetization, the critical current density and the m
icrostructure of the high-temperature superconductor La1.85Sr0.15CuO4
are compared. Direct observations by transmission electron microscopy
(TEM) revealed two orthogonal arrays of extended screw-type dislocatio
ns (2 to 5 x 10(11) lines per cm2) parallel to the crystallographic di
rections [100] and [010], respectively. These dislocations are dissoci
ated into partial bound stacking faults. Microanalysis showed that Sr
concentration around the dislocation cores is about 10% lower than tha
t of the matrix. Measurements of the hysteresis cycle, M(H, T), at var
ious angular orientations (theta.phi) of the field H with respect to t
he crystalline directions show no detectable correlation between the d
irections of the dislocations and the critical current density. This s
uggests that the anisotropy of the critical current density is first o
f all controlled by the intrinsic properties of the material rather th
an by the anisotropy of the dislocation structure.