Improvement of critical current density in the Cu/MgB2 and Ag/MgB2 superconducting wires using the fast formation method

摘要

The powder in tube method has been used to fabricate Ag and Cu clad MgB2wires using an in-situ reaction method. The effects of short time sintering onthe critical current densities of Ag and Cu clad MgB2 wires were studied. Allthe samples were examined using XRD, SEM, and magnetization measurements. ForAg clad wire Jc is improved by more than two times after the short timesintering process. Jc values of 1.2x10^5 A/cm2 in zero field and above 10^4A/cm2 in 2T at 20 K have been achieved for Ag clad MgB2 wire which is onlysintered for 6 minutes at 800oC. However, a remarkable degree of reaction hasbeen found between the superconducting cores and the sheath materials, leadingto the formation of Cu2Mg and Ag3Mg for copper and silver clad wires,respectively. The results from Tc, Jc and Hirr convincingly show that the shortsintering causes less reaction between the magnesium and the sheath materialsand markedly improves the critical current density. Our result shows that Ironis still the best sheath material because of the lack of reaction between Feand the superconducting MgB2 material.