Transport critical current density above at 77 K in superconducting tapes made by the Ag wire-in-tube method

Abstract

Transport critical current density (J c ) is a limiting factor in the practical application of (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O y (BSCCO-2223) high-temperature superconducting materials. The minimum requirement is for a J c of 10 5 A cm −2 in long wires and tapes, at 77 K and in a high magnetic field. The issue of current distribution inside Ag-sheathed tapes has been resolved by showing that the region of high critical current density is next to the silver. In this paper we report a J c value > 10 5 A cm −2 at 77 K in a self-field in Bi 1.8 Pb 0.4 Sr 2.0 Ca 2.2 Cu 3.0 O y superconducting tapes made by the Ag wire-in-tube method, in which a silver wire was introduced into the silver tube. The silver wire extended along the entire length of the tape and reduced the difference between the nominal cross section of the superconductor and its actual current-carrying cross section. At 77 K and self-field, a maximum J c of 2 × 10 5 A cm −2 (critical current I c = 22 A) was measured after three pressing cycles at 800 • C in a 7% O 2 atmosphere. The average thickness of the superconducting layer between the sides of silver layers was in the order of 1-2 µm and the width was 3.6 mm. This study confirms that the current-carrying region in BSCCO tapes is the layer adjacent to the Ag sheath. Previously it was shown that the superconductor core for thicker superconductor layers (∼ 70 µm) does not carry significant current.

The effect of cooling rates on transport current properties and the critical temperature of Ag-sheathed BSCCO-2223 superconducting tapes

“…By deconstructing tapes it was demonstrated that the thin layer of superconductor (about 10 µm) remaining on the silver sheath carried the same I c as did the intact tape [3]. These transport measurements resulted in a J c value greater than 10 5 A cm −2 at 77 K. Magnetization measurements on deconstructed tapes also confirmed the very high J c values in the thin layer of superconductor near the Ag sheath [4]. J c values greater than 10 6 A cm −2 were measured at 10 K. Tapes with a single Ag wire replacing the bulk of the central core of the superconductor were made [5].…”

The effects of hydrostatic pressure on the BSCCO compound for the OPIT procedure

“…The J c values for short pieces of SF tapes reflect an improvement by a factor of 2.9 in the last three years and they are 69 kA cm −2 [1,2] and 200 kA cm −2 [3] at 77 K and under the self-field. For technologically practical, MF long tapes (> 100 m) progress between 1992 and 1994 led to an improvement by a factor of 2.5, from > 10.5 kA cm −2 [4] to 26.5 kA cm −2 [5].…”

Processing and characterization of Ag-clad Bi-2223 superconductors

“…Existence of such a layer has been confirmed by microslice experiments [4], high-resolution transmission electron microscopy [SI, and magneto-optical imaging [6]. Based on these results and the ever increasing demand for conductors with high current transport properties, effort was made to develop superconducting tapes by the Ag wire-in-tube (WIT) method.…”