Evidence for preferential formation of the (Bi,Pb)2Sr2Ca2Cu3Ox phase at the Ag interface in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox tapes

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Abstract
Studies of the phase evolution in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox (2223) tapes processed with fine aerosol spray pyrolysis powder show that the 2223 phase always forms preferentially at the Ag interface at temperatures lower than those needed to form 2223 away from the Ag. The 2223 basal planes align themselves with the Ag surface and 2223 can penetrate into the Ag where the interface undulates. In the interior of the Bi-Sr-Ca-Cu-O core, away from the Ag, reaction to alkaline earth cuprate is favored over reaction to 2223. These results provide direct evidence of the beneficial role that Ag plays in developing the 2223 phase and emphasize the need to produce smooth Ag interfaces to attain highly aligned 2223.