Fabrication, Properties, and Microstructures of High-Tc Tapes and Coils Made from Ag-Clad Bi-2223 Superconductors
Pb0.4Bi1.8Sr2Ca2.2Cu3Ox (Bi-2223) precursor powders were prepared via a solid-state reaction of carbonates and oxides of Bi, Pb, Sr, Ca, and Cu. Our results indicate that an in-situ reaction between constituent phases, accompanied by the formation of a transient liquid that is consumed during final heat treatment, is essential to obtain increased density with greater connectivity between the 2223 grains. Relative amounts of the constituent phases were adjusted in the powder by varying the calcination conditions, and the powder was then used to fabricate Ag-clad tapes by the powder-in-tube technique. With the improving process conditions, transport critical current density values greater than 4 × 104 A/cm2 at 77 K and 2 × 105 A/cm2 at 4.2 and 27 K have been obtained in short tape samples. Long tapes were cut into lengths up to 10 m long and used in parallel to fabricate small superconducting pancake coils. The coils were characterized at 77, 27, and 4.2 K and the results are discussed in this paper.
KeywordsCritical Current Density Constituent Phasis Final Heat Treatment High Critical Current Density Conductor Tape
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