The effect of Ag wire shape on the microstructure and Jc performance of BPSCCO-2223/Ag wire composite bulks

Abstract

To improve the superconducting properties of (Bi,Pb)2Sr2Ca2Cu3Oy (BPSCCO-2223) superconductors, we investigate the microstructure and critical current density (Jc) performance at 77.3 K under self-field and/or 4.2 K under several magnetic fields on BPSCCO-2223 bulk composed of silver (Ag) wires with diameters of 0.2 mm and 0.4 mm. The composites of Ag wires are hand-made by stacking Ag wires into the oxide powder in the direction of thickness alternately, and then the prepared samples are sintered at 840 °C for 50 h. In this study SEM and EPMA observation results show that good c-axis oriented and densely structured BPSCCO-2223 plate-like grains can be formed around the interfacial region between BPSCCO-2223 oxide and metal Ag regardless of the diameter of Ag wire. The Jc values of the sample composed of Ag wires are higher than those of the sample without Ag wires. The Jc values of the sample composed of 0.4 mm Ag wires are higher than those of the sample composed of 0.2 mm Ag wires, and then these values improved further by increasing the number of Ag wires regardless of their diameter under several measurement conditions. The maximum Jc values are estimated about 300 A cm−2 at 77.3 K under self-field, and 1200 A cm−2 at 4.2 K under self-field when composed of 24 0.4 mm Ag wires. These Jc values are about two to three times higher than those of the bulk without Ag wire.