The reactions of Bi(PbSrCaCuOAg supercnducting microcomposites placed in contact with silver, gold, palladium, nickel, copper and platinum substrates

Abstract

Abstract Bi(Pb)SrCaCuOAg (BSCCO-Ag) superconducting microcomposites were produced by oxidation, annealing and deformation of metallic precursor alloys. Silver, gold, palladium, nickel, copper and platinum sheets have been used to produce two-dimensional superconducting composites via deformation-annealing processes. The reactions between BSCCO-Ag and these metallic elements and the effects of these reactions on the superconducting properties of the BSCCO-Ag microcomposites were studied by a combination of microstructural observation and microanalysis. Silver, gold and palladium do not oxidize at elevated temperatures, and they have very little or no reaction with BSCCO-Ag microcomposites. Microcomposite specimens in contact with silver, gold and palladium sheets possess a high T c (T R=0 = 102−108 K ) and reasonably good J c (J c(77 K ) = 400−1000 A cm −2 ) . The microstructure of these samples showed a well-developed textured 2:2:2:3 phase embedded in the silver matrix. Nickel and copper partially or fully oxidized under the annealing conditions. These elements reacted with BSCCO, prevented the formation of the 2:2:2:3 phase and resulted in a 2:2:1:2 phase dominant microstructure with lower T c (T R=0 ≈75 K ) . Platinum entered the silver phase in the BSCCO-Ag microcomposites, forming AgPt solid solutions, and reacted with the BSCCO compounds to form several complicated oxide phases. Thin silver sheets have been successfully used to separate BSCCO-Ag and stainless steel and thereby to prevent reactions between stainless steel and the microcomposite.