无定形C掺杂对MgB_2微结构和超导电性的影响

Effect of Amorphous Carbon-Doping on Microstructure and Superconductivity of MgB_2 Wires

采用原位法粉末装管工艺制备了MgB2-xCx/Nb/Cu单芯线材.通过X射线衍射(XRD)、扫描电镜(EMS)和物性测试仪(PPMS)等手段研究了无定形C掺杂对线材微观结构及超导电性的影响.结果显示,随着C掺杂量的增加,进入MgB2晶格的C含量增加,MgB2层间结构不变.样品性能达到实用化超导磁体要求,在温度30 K外场0.2 T条件下,C掺杂量x=0,0.05,0.10,0.15的样品临界电流密度分别达8.1×104,1.7×105,1.6×105和1.0×105A/cm2.实验表明最佳C掺杂量x在0.05与0.10之间.

The amorphous carbon-doped MgB2-xCx/Nb/Cu single-core wires were prepared by in-situ PIT（powder in tube） method,where the C-doping content x=0,0.05,0.10 and 0.15.Phase formation and microstructure of the wire samples with different doping contents were analyzed by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and so on.It was found that the C content entering into MgB2 lattice increases with increasing carbon doping content,while the interlayer structure of MgB2 changes little.Electric properties of the samples showed that they meet the practical requirements of superconducting magnet,i.e.,the critical current density of samples is 8.1×104,1.7×105,1.6×105 and 1.0×105 A/cm2 at 30 K in the 0.2 T external electromagnetic field when the C-doping content x=0,0.05,0.10 and 0.15,respectively.As shown by the experimental results,the optimum C-doing content x ranges from 0.05 to 0.1.