Properties of (Hg,X)-1223 superconductors synthesized without using a glove box

Abstract

We tried to synthesize (Hg,X)BazCa,.iCu,,O, (HgX-12(n-l)n) superconductors for the substitution of various elements X without using a glove box. For X=V, Cr, Mn, Ge, MO, Ru and Re, we succeeded in the formation of the phases of n=2,1,2,1,3,3 and 3, respectively. It is suggested that the substitution of X for Hg is effective to stabilize the structures of HgX-12(n-l)n phases. Studies of microstructure and superconducting properties on HgMo-and HgRe-1223 revealed that the melt texturing was observed only for MgMo-1223 and that the Tc's of both samples were above 130 K, almost equal to that of Hg-1223. The irreversibility fields of HgMo-and HgRe-1223 were roughly estimated to be about 1.6 and 3 T at 90 K, respectively. These values are higher than that of Hg-1223. It is speculated that this enhancement is due to the improved coupling of Cu-0 planes by the contraction of c-axis or the carrier doping by oxygen atoms introduced in the Hg-(0) layer.

Enhancement of critical current density ofin situprocessed MgB2tapes by WB addition

“…All the tapes showed relatively sharp transitions. The T c was 35.7 K for x = 0, which is lower than that of the bulk material with a T c of 39 K. This lower T c is due to the poor crystallinity of samples caused by the lower-temperature heat treatment [8]. The T c shifted to a lower temperature by the addition of WB.…”

“…One is an ex situ method, in which commercially available or self-prepared MgB 2 powders are packed into a tube [2][3][4][5]. The other is an in situ method, in which constitute powders, such as Mg and B, are packed into a metallic tube, and then, the MgB 2 phase is formed inside the tube by a heat treatment [6][7][8]. The in situ processed tapes showed lower transport critical current density (J ct ) values due to the lower density of the MgB 2 core layer.…”

“…The in situ processed tapes showed lower transport critical current density (J ct ) values due to the lower density of the MgB 2 core layer. The density of the core layer has been successfully improved by using a powder mixture of MgH 2 + B as a precursor, and the J ct of tapes obtained is 3 kA cm −2 at 4.2 K and 10 T [8]. However, this value is still very low for practical applications.…”