Preparation of Ag-Sheathed (Tl, Bi)-Ca-Sr-Cu-O Superconducting Wire

Abstract

In the Tl-Bi-Ca-Sr-Cu-O system, Tl-O single layered superconducting phases of (Tl, Bi)CaSr2Cu2O x and (Tl, Bi)Ca2Sr2Cu3O x have been obtained. We prepared Ag-sheathed wire using the oxide powder of the (Tl, Bi)Ca2Sr2Cu3O x phase with T c of 113 K. With a decrease in the thickness of the rectangular wire specimen, J c at 77 K increases rapidly, reaching a maximum value of 1.45×104 A/cm2 at 0.05 mm in thickness. The crystal structure, morphology and microstructure of the superconducting core of the wire were observed using XRD, SEM and TEM to investigate the cause of the J c enhancement.

Liquid phase sintering and microstructure development of Ag-clad Tl-1223 superconductor

“…For purposes of comparison, all tapes were rolled under the same conditions. Investigators have found that J c values of PIT tapes are inversely proportional to tape thickness until core uniformity is degraded at very small thickness [18], and that J c increases by one order of magnitude when tape thickness is reduced to 50 µm [19]. The tapes in the present study were rolled to a final thickness of 300 µm, below which core uniformity was lost.…”

Tl-based superconductors for high-current, high-field applications

“…Because of the higher irreversibility line of the Tl-1223 system when compared to that of Tl-2223, a significant effort has been devoted mainly to the development of Tl-1223 tape wire [11,12,24,25,[36][37][38][39][40][41][42][43][44][45][46]81]. In order to stabilize the 1223 phase and to optimize the weak links and pinning properties of the two basic Tl-Ba-Ca-Cu-O and Tl-Sr-Ca-Cu-O compounds [12,24,35,36], various types of structural substitutions have been gradually applied [11,25,[37][38][39][40][41][42][43][44]81] from which the best known are those with Tl-sites partially replaced by Pb or Bi, or by both, and the Sr-sites partially or entirely substituted by Ba. In one case, the partial replacement of Tl by V and Sr by Ba has been reported [39].…”

“…However, a small change in the Sr/Ba of 1.6/0.4 caused a dramatic decrease in J c even without any external magnetic fields. Using also the results of other authors, [41] (table 1, number 1) instead of a partial substitution of Tl by Pb, they partially substituted Tl with Bi to prepare (Tl 0.78 Bi 0.22 )(Sr 0.8 Ba 0.2 ) 2 Ca 2 Cu 3 O x / Ag tape samples (table 1, number 5). In order to investigate a possible improvement of both the alignment and closer contact of grains, a uniaxial compression of rolled final tapes was applied and its effect upon the eventual J c improvement studied (the dr-ro-si and pr-si method) [44].…”