Abstract
Fabricating long lengths of robust and high-quality conductors is imperative for the various applications envisaged for high temperature superconductors (HTS). The powder-in-tube technique has been successfully used to transform the HTS based compounds to a more useful form such as wires and tapes. In the present study Bi-2212 and Yb-123 silver-clad tapes were fabricated using the PIT technique which comprised of groove and flat rolling. The tapes were processed by subjecting them to appropriate melt processing treatments. In the case of Bi-2212 tapes the effect of processing atmosphere (air vs. oxygen) on the current transport properties and microstructure were studied. The average J(c) at 4.2 K, self-field with I muV/cm criteria, was higher for tapes processed in oxygen (5 x 10(4) A/cm(2)) compared to the tapes processed in air (6.25 x 10(3) Amp/cm(2)). Detailed microstructural analysis have been conducted using SEM, WDX, and TEM.
The Yb-123 tapes were melt processed by passing them through a zone-melting furnace at a controlled rate, In this case the effect of oxygen partial pressure (pO(2)) on the phase formation and current transport properties of the tapes were evaluated. The tapes were processed in 0.21, 0.01, and 0.001 atm, respectively. Highest J(c) of 20,000 A/cm2 at 4.2 K and self field was achieved for the tapes processed in a pO(2) Of 0.001 arm. Poor current transport properties of tapes processed in air and 0.01 atm can be attributed to the presence of unreacted BaCuO2, CuO, 211 and voids in the superconductor core.