CHEMICAL WEAK-LINK MODIFICATION RESPONSIBLE FOR HIGH INTERGRAIN-J(C) IN BI-BASED 2223-SUPERCONDUCTING CERAMICS PREPARED BY THE GLASSY ROUTE

Bi1.7Pb0.3Sr2Ca2Cu3O10-y samples prepared by the glass precursor route were examined. A.c. susceptibility properties were studied and compar ed to those of samples obtained by the solid-state route. The intercon nected lattice of 2223 needle-like grains in a matrix of strontium, ca lcium, and copper small and globular precipitates of irregular shape l eads to an interesting behaviour of the critical current density as a function of d.c. field: there is high intergrain J(c) and weak field d ependence (J(c) > 10(5) A/cm2 at 77 K and 0 T), in contrast to J(c) va lues and field dependence of classical solid-state route samples. It c an thus be claimed (unambiguously now) that the intricate superconduct ing grain boundary structure acts as the ingredient for improved pinni ng at low d.c. field at least in such systems.