Large Jc enhancement in Bi-2212/Ag multilayer tapes by the PAIR process

An overview of J(c) enhancement, high field performance, and an optimization of conductor design of Bi2Sr2CaCu2Ox (Bi-2212)/Ag PAIR (Pre-Annealing and Intermediate Rolling) processed tapes are described in this paper. The major key to the large J(c) enhancement achieved by the PAIR process is the improvements of both microscopic and macroscopic uniformity. It leads to the Bi-2212 phase formation occurring near the equilibrium, resulting in Bi-2212 layers with an excellent grain alignment, no impurity phase, and an excellent J(c) value. J(e) values of short specimens cut from 100-m-long PAIR tape are 380-450 A/mm(2) and 330-390 A/mm(2) at 4.2 K in 22 T and 30 T, respectively. Design of conductor geometry was optimized based on the relationship between Bi-2212 layer thickness and J(c) for monolayer Bi-2212/Ag tapes. J(e) of Bi-2212/Ag multilayer tapes (4 mm tape width, 25 mu m thick Ag substrate, 4 Bi-2212 layers, 20-30 Ccm thick Bi-2212 layer) is estimated as 1200 A/mm(2) (4.2 K, 10 T). J(e) of 500-600 A/mm(2) at 4.2 K, 20 T can be expected for an optimized long tape. This excellent J(e) indicates that PAIR tapes are potential for practical applications. PAIR tape has a large possibility to be used for high-field insert coils. (C) 2000 Elsevier Science B.V. All rights reserved.