Fabrication of (Bi,Pb)-Sr-Ca-Cu-O superconductors

Bi-Sr-Ca-Cu-O superconductors were discovered approximately one year after the YBa2Cu3O7-y(123) material which was the first to display a superconducting transition temperature (Tc of 93degK) above that of the boiling point of liquid nitrogen. Bi2Sr2Ca2Cu3O10-y(2223; n = 2) has a higher Tc(110degK) than 123 and belongs to the family of superconducting compounds Bi2Sr2CanCun+1O6+2n-y, while the more easily-formed Bi2Sr2CaCu2O8 (2212, n = 1) has a Tc of 80degK. The present work is ultimately directed at the development of devices using wires and cables. For the formation of such bulk materials having good mechanical and electrical properties we are principally interested in the Bi group rather than 123 because of the difficulty experienced of oxygenating the 123 sample interior. We will focus on the following aspects of the Bi-Sr-Ca-Cu-O superconductors: (a) optimum routes to 2223, (b) densification, (c) formation of tapes by the doctor blade method