INTRODUCTION OF PINNING CENTERS INTO BI-(PB)-SR-CA-CU-O SUPERCONDUCTORS

High critical current density (J(c)) is essential for most large-scale applications of high-temperature superconductors (HTSs). In addition to the weak link problem, weak flux pinning is a major cause of the ra pid decline of J(c) with magnetic field at high temperatures. Through intensive research in the past 10 years the weak pinning problem has b een partially overcome and J(c) has reached a level approaching the re quirement for some commercial applications. In this article, a number of techniques by which effective pinning centres can be introduced to improve flux pinning in Bi-(Pb)-Sr-Ca-Cu-O HTSs are reviewed. These in clude surface pinning through a spiral growth, fine precipitates produ ced through phase transformation or phase formation-decomposition, inc lusions ih ro ugh chemical doping or addition, cascades and columnar d efects created by fast-neutron and heavy ion beam irradiation and vari ous defects induced by mechanical deformation. In particular, the resu lts of Bi-2223 :formation-decomposition and cold deformation versus ho t deformation have a significant implication for HTS wire fabrication. Comparative studies with comprehensive electrical, magnetic and micro structural characterizations have been carried out to assess ii-re eff ectiveness of these techniques.