Wet spinning of a single layered perovskite Y-Ba-Cu-O superconductor

Abstract

Recently high T c oxide superconductors such as Y B a C u O system with a Tc more than 90 K were successively discovered [1, 2]. Such oxide superconductors are usually brittle and difficult to fabricate into tapes or wires, which are useful in large scale engineering applications of superconducting magnets, power transmission lines, etc. We have studied the preparation of an oxide superconducting filament using a low cost textile fibre spinning technology [3, 4]. In a previous paper suspension spinning of the precursor to the Y Ba-Cu oxide was studied. The viscous precursor to the Y B a C u oxide was extruded as a filament, dried and subjected to heat treatment to remove volatile components and to generate oxide in the layered perovskite phase. In this paper, a suspension spinning of the single layered perovskite Y B a C u oxide was studied to prepare the long superconducting filament with high To. The mixed powder specimen with nominal composition Y1Ba2Cu3Og_6 was initially prepared by mixing high purity, fine powders of Y203, BaCO3 and CuO, grinding and heating them at 1223 K for 18 ksec in oxygen and cooling to room temperature at a cooling rate of 100 K h ~ in oxygen. The resultant pellet had a single layered perovskite phase [5] and was a superconductor with Tc greater than 82 K. The pellet was ground and filtered through 846 meshes to make a fine powder of less than 15 #m in diameter. The powder was suspended in an aqueous solution containing a dispersant. The mixture of poly(oxyethylene(23) lauryl ether) and sodium dodecyl sulphate was used as the dispersant. The suspended powder was added to a poly(vinylalcohol) (PVA) aqueous solution containing the dispersant. The spinning dope was extruded as a filament into a precipitating medium of mixed aqueous solution of 20 g NaOH 1-1 and 400 g Na2 SO4 1 l at 313K and was coiled on a winding drum at a low winding speed of 1 m sec-l. The filament was then neutralized by steeping in a mixed aqueous solution of 100g H z S O 4 1 l and 300g Na2SO41 -l , washed and dried. A long filament more than 80#m in diameter was obtained. The filament consisted of up to 95 wt % powder content. The tensile strength of the