Enhancement of superconducting properties of Bi-based oxide high T-c thick films using nanosized crystals as flux-pinning centers

The use of nanosized crystals as flux-pinning centers to improve the critical current density (J(c)) - magnetic field (H) dependence of Bi-oxide high transition temperature (T-c) superconducting thick films was studied. It is demonstrated that the controlled introduction of (Sr, Ca)(14)Cu24O41+x needle-like defects into Bi2Sr2CaCu2O8+x/Ag composite tapes improved the J(c) in magnetic fields from 0 to 1 T from 20 - 60 K. The experimental data was also consistent with the inclusion flux-pinning model J(c) Const V-f/d, where the critical current density increases as the defect size is reduced; or the volume fraction of defects is increased. (C) 1997 Acta Metallurgica Inc.