Superconducting Property of<tex>$hboxNb_3(hboxAl,hboxGe)$</tex>Conductors Prepared by Diffusion Process

Abstract

Nb 3 (Al Ge) conductors were prepared with a diffusion reaction process at a temperature around 1400 C, from multifilamentary Nb/Al-25at%Ge precursors. Critical current densities of 300 A mm 2 at 21 T and 220 A mm 2 at 23 T at 4.2 K have been obtained after a diffusion reaction at 1400 C for 7 h followed by 10 h/800 C heat treatment. The c2 in excess of 28.5 T is about 2 T larger than that of the so-called RHQT Nb 3 Al. Large Al-Ge filament size in the precursors over a few microns might be acceptable to improve high-field c performance, significantly reducing fabrication difficulty of the Nb/Al-Ge precursors. Small matrix ratio of 0.8 and piece-length of 30 m was achievable in the precursor preparation at our laboratory workshop without intermediate annealing. In addition, the current capacity up to values higher than 300 A at 21 T, 4.2 K has been given by an enlarged cross-section sample.Index Terms-Diffusion process, high-field material, Nb 3 Al, Nb 3 (Al Ge).

Phase formation and superconducting properties of mechanically alloyed Nb3(Al1−xGex) system

“…By further increasing T s to 1100 °C and 1200 °C, the amount of the superconducting phase does not increase much but the T c value improves significantly from <11 K to 14.4 K, and even to 17.7 K, respectively. The T c value of 17.7 K is close to that achieved by the RHQT method [13]. This reveals that in this stage the crystal structure as well as the electronic structure of the Al5 phase has been optimized.…”

“…In order to further illuminate the properties of the mechanically alloyed Nb 3 (Al 0.75 Ge 0.25 ) superconductor, figure 9 shows the magnetization hysteresis loops at 4.2 K, 6 K, 8 K and 10 K for the Nb 3 (Al 0.75 Ge 0.25 ) sample sintered at T s = 1200 °C. The sample shows a weak flux jump in the low field region which is not as strong as that observed in Nb 3 Al wires prepared by the RHQT method [5][6][7][8][9][10][11][12][13]. A possible reason may be that the sample used in this study is a bulk one which is not as dense as the Nb 3 Al wires.…”

“…In the past few years excellent Nb 3 Al wires have been produced by the rapid heating, quenching and transformation (RHQT) method [3][4][5][6][7][8], arc-melting [1,9] and thin-film deposition [10], but a practical fabrication process for developing commercially available long-length Nb 3 (Al 1 −x Ge x ) wires with high performance has not yet been established because of the poor workability of the Al-Ge alloy [11], the requirement of specialized instruments to provide extremely high reaction temperatures of about ∼2000 °C in the RHQT technique, and other unsolved problems [5,12,13].…”

Enhancement of Critical Current Density of Nb3Al Superconductors by B Doping

“…After determining the existing form of the doped B, it is apparent that B doping is different from Sn doping, and Ge doping in Nb 3 Al. [18,19,32] When designing this experiment, the element ratio of Ge doping and Sn doping were used for reference, that is, taking a mass amount of Al out and adding with a corresponding molar mass of B. For Ge doping and Sn doping, Ge and Sn can replace Al to maintain the structural integrity of Nb 3 Al.…”