after a thermal treatment at 700 °C for 1 h were fitted using a multiphase Rietveld refinement. Although the resulting powders are composed mainly by Nb3Sn (up to 87 weight%), certain amount of otherintermetallic phases like Nb6Sn5, NbSn2 and Nb and Sn oxides were also determined. In agreement with the Rietveld refinement analysis, microprobe analysis also revealed that changes in chemical composition
摘要 本研究采用粉末冶金法合成了纳米尺寸晶粒的金属间化合物Nb3Sn。将化学计量比例的 Nb 和 Sn 元素粉末在氩气保护气氛下在高能磨机中机械合金化 3 小时。研磨粉末的 X 射线衍射图证实了 Nb(Sn) 固溶体的形成,这证明仅存在 Nb 峰,这些峰向更高的角度移动。用于分析此 XRD 图案的 Rietveld 改进表明,当使用空间群为 I4/mmm 的四方结构代替空间群为 Im-3m 的 Nb 立方晶格时,拟合效果更好。通过使用“双 Voigt”方法对峰轮廓进行线加宽的尺寸应变分析表明,加宽是由于小晶粒尺寸(约 6 nm)和微应变造成的。为了形成 Nb3Sn 有序相,需要对 Nb(Sn) 粉末混合物进行后续热处理。使用多相 Rietveld 精修拟合在 700°C 下热处理 1 小时后获得的 X 射线衍射图。虽然所得粉末主要由 Nb3Sn(高达 87 重量%)组成,但也确定了一定数量的其他金属间相,如
Characteristics of a production route for filamentary Nb3Sn superconductors based on a reaction between niobium and Nb6Sn5
作者:W.L. Neijmeijer、B.H. Kolster
DOI:10.1016/0022-5088(90)90118-4
日期:1990.4
Some progress in metallic superconductors in Japan
作者:K. Tachikawa
DOI:10.1016/0921-4526(95)00481-5
日期:1996.1
Bronze-proceeded Nb3Sn with Ti addition to the matrix is being widely used for generating high magnetic fields. Ge doping to the matrix also enhances J(c) of Nb3Sn in high fields. Nb3Sn synthesized from Nb6Sn5 compound shows appreciably better high field performance than that of bronze-processed Nb3Sn. Nb3Al and Nb-3(Al, Ge) wires are being developed through different processes as alternative high-field superconductors for Nb3Sn. An AC test coil using a new ultrafine filamentary Nb-Ti wire with a Cu-Si alloy matrix has been successfully operated. The AC performance of bronze-processed Nb3Sn has been improved by Ge addition to the matrix. Meanwhile, cryogen-free superconducting magnets using Nb3Sn or Nb-Ti wire have been realized by applying high T-c Bi-2212 or 2223 current lead.