E. Mendoza et al., Critical current enhancement in YBCO-Ag melt-textured composites: influence of microcrack density, PHYSICA C, 334(1-2), 2000, pp. 7-14
A strong increase of the critical current density of YBa2Cu3O7 (YBCO) melt-
textured composites has been observed by adding Ag2O particles in the precu
rsor mixture while the concentration of Y2BaCuO5 (Y211) precipitates remain
s constant. Critical current density enhancement factors as high as 200% at
5 K (J(c)(ab)(5 K, 0 T) similar to 2.5 x 10(6) A/cm(2)) and 1000% at 77 K
and 2 T (J(c)(ab)(77 K, 2 T) similar to 2.2 x 10(4) A/cm(2)) have been reac
hed in samples with 20 wt.% of Ag2O. Critical current measurements at 77 K
for H parallel to ab also confirm the increase of the J(c) enhancement fact
or with the magnetic field (similar to 100% at 0 T and 140% at 2 T). The im
provement of the critical currents in the YBCO-Ag melt-textured composites
is correlated with the reduction of the density of microcracks parallel to
the ab plane, as observed by scanning electron microscopy (SEM). Results ar
e interpreted in terms of a release of the current limiting factors and an
improvement of flux pinning properties by preexisting defects. (C) 2000 Els
evier Science B.V. All rights reserved.