Zhang Danlu, Wan Fang, Sumption Michael D, Collings Edward W, Thong C J, Rindfleisch Matt, Tomsic Mike
CSMM, Materials Science and Engineering, The Ohio State University, Columbus, OH 43220, USA.
Hyper Tech Research Inc., Columbus, OH 43228, USA.
IOP Conf Ser Mater Sci Eng. 2020 Jul;756. doi: 10.1088/1757-899x/756/1/012019.
MgB superconducting wires and bulks with nano-LaO addition have been studied. A series of MgB superconducting bulk samples with nano-LaO addition levels of 0, 5, 7, 18wt% were prepared. AC resistivity data showed slight increases of and unchanged for the bulk samples with doping levels lower than 7 wt% and decreased critical fields for the heavily doped (18 wt%) bulk. X-ray diffraction (XRD) showed the presence of LaB in the nano-LaO doped MgB bulk samples and decreased MgB grain size in nano-LaO doped bulks. Monocore powder-in-tube (PIT) MgB wires without and with 5 wt% nano-LaO addition (P-05) were prepared for transport property measurement. 2mol%C-doped (SMI) boron powder was used for wire P-05 and previously prepared control wires (control wires were made without the addition of nano-LaO powder, W-00 and P2). Low field magnetic properties were obtained from magnetization loop (M-H), transport critical current density ( ) was measured at 4.2 K for the nano-LaO doped PIT wire (P-05) and the control samples (P2 and W-00). The transport critical current density (B) of P-05 at 4.2 K and 8 T (6.0 ×10 A/cm) was twice that of the control wire. The critical magnetic fields ( and ) of P-05 and the control sample P2 were compared. The critical fields of P-05 were slightly less than those of P2. Kramer-Dew-Hughes plots indicated a change from surface pinning to a mixture of volume pinning and surface pinning. It is shown that enhancement of P-05's transport properties is due to additional flux pinning by the fine-size rare-earth borides rather than enhanced or .
对添加了纳米LaO的MgB超导线材和块材进行了研究。制备了一系列纳米LaO添加量分别为0、5、7、18wt%的MgB超导块材样品。交流电阻率数据表明，掺杂水平低于7wt%的块材样品，其电阻略有增加且临界温度不变，而重掺杂（18wt%）块材的临界场强降低。X射线衍射（XRD）显示，在纳米LaO掺杂的MgB块材样品中存在LaB，且纳米LaO掺杂块材中MgB晶粒尺寸减小。制备了未添加和添加5wt%纳米LaO（P-05）的单芯粉末装管（PIT）MgB线材，用于传输性能测量。2mol%C掺杂的（SMI）硼粉用于制备线材P-05以及之前制备的对照线材（对照线材在制备时未添加纳米LaO粉末，W-00和P2）。通过磁化回线（M-H）获得低场磁性能，在4.2K下测量了纳米LaO掺杂的PIT线材（P-05）以及对照样品（P2和W-00）的传输临界电流密度（ ）。P-05在4.2K和8T（6.0×10 A/cm）时的传输临界电流密度 （B）是对照线材的两倍。比较了P-05和对照样品P2的临界磁场（ 和 ）。P-05的临界场强略小于P2。克莱默-德休斯曲线表明从表面钉扎转变为体钉扎和表面钉扎的混合。结果表明，P-05传输性能的增强是由于细尺寸稀土硼化物产生的额外磁通钉扎，而非 或 的增强。
