Yang Y, Sumption M D, Rindfleisch M, Tomsic M, Collings E W
Center for Superconducting and Magnetic Materials, Department of Materials Science and Engineering, the Ohio State University, Columbus, OH 43210, United States of America.
Western Digital, San Jose, CA, United States of America.
Supercond Sci Technol. 2021 Feb;34(2). doi: 10.1088/1361-6668/abc73c. Epub 2021 Jan 12.
Bulk samples of magnesium diboride (MgB) doped with 0.5 wt% of the rare earth oxides (REOs) NdO and DyO (named B-ND and B-DY) prepared by standard powder processing, and wires of MgB doped with 0.5 wt% DyO (named W-DY) prepared by a commercial powder-in-tube processing were studied. Investigations included x-ray diffractometry, scanning- and transmission electron microscopy, magnetic measurement of superconducting transition temperature ( ), magnetic and resistive measurements of upper critical field ( ) and irreversibility field ( ), as well as magnetic and transport measurements of critical current densities versus applied field ( () and (), respectively). It was found that although the products of REO doping did not substitute into the MgB lattice, REO-based inclusions resided within grains and at grain boundaries. Curves of bulk pinning force density ( ) versus reduced field ( = / ) showed that flux pinning was by predominantly by grain boundaries, not point defects. At all temperatures the () of W-DY experienced enhancement by inclusion-induced grain boundary refinement but at higher temperatures () was still further increased by a DyO additive-induced increase in of about 1 T at all temperatures up to 20 K (and beyond). It is noted that DyO increases and that it does so, not just at 4 K, but in the higher temperature regime. This important property, shared by a number of REOs and other oxides promises to extend the applications range of MgB conductors.
研究了通过标准粉末工艺制备的掺杂0.5 wt%稀土氧化物（REOs）NdO和DyO的二硼化镁（MgB）块状样品（分别命名为B-ND和B-DY），以及通过商用管内粉末工艺制备的掺杂0.5 wt% DyO的MgB线材（命名为W-DY）。研究内容包括X射线衍射、扫描电子显微镜和透射电子显微镜、超导转变温度（ ）的磁性测量、上临界场（ ）和不可逆场（ ）的磁性和电阻测量，以及临界电流密度与外加磁场（分别为 （）和 （））的磁性和输运测量。结果发现，尽管REO掺杂产物并未替代MgB晶格，但基于REO的夹杂物存在于晶粒内部和晶界处。块状钉扎力密度（ ）与约化场（ = / ）的曲线表明，磁通钉扎主要由晶界而非点缺陷引起。在所有温度下，W-DY的 （）因夹杂物诱导的晶界细化而增强，但在较高温度下， （）在高达20 K（及更高）的所有温度下仍因DyO添加剂导致的 增加约1 T而进一步增加。值得注意的是，DyO增加了 ，而且不仅在4 K时如此，在较高温度范围内也是如此。许多REOs和其他氧化物都具有的这一重要特性有望扩展MgB导体的应用范围。
