Influence of Nb Diffusion Layer on Superconductivity of MgB2/Nb/Cu Wires

摘要:

采用原位法粉末装管工艺（in-situ PIT），以Nb/Cu复合管作为包套材料制备了MgB2超导线材并且在氩气保护气氛中，不同温度条件下保温2 h进行成相热处理。分别采用电阻-温度测试、磁矩转变测试、临界传输电流测试以及Nb-MgB2界面磁光研究等分析手段进行研究。结果表明：当热处理温度高于750 ℃时，在MgB2超导芯丝和Nb阻隔层之间形成一个扩散层，该扩散层的存在阻碍了电流的传输，从而导致在磁测法测试中可以检测到超导相存在，而在传输法测试中无法看到超导传输现象。说明采用Nb作为MgB2超导线带材的扩散阻隔层时其热处理温度不能高于750 ℃

Abstract:

The MgB2 wires were prepared by in-situ Powder-in-Tube (PIT) method with Nb/Cu compounds tube as the sheath and then were heat treated at various temperatures for 2 h in flowing argon. The resistivity (R-T), magnetic moment (M-T), transport critical current (Ic-B) and magneto optical (MO) properties of MgB2 wires were analyzed. The results show that there is a diffusion layer between MgB2 superconducting core and Nb barrier layer when the heat-treatment temperature is higher than 750 °C, and this diffusion layer obstructs the current transfer into MgB2 superconductor core from the Cu sheath. This indicates that the best heat-treatment temperature for the MgB2 wires with Nb as the barrier layer should be lower than 750 °C