Superconducting property of Nb3(Al, Ge) conductors prepared by diffusion process

Nb₃(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/mm² at 21 T and 220 A/mm² 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 H_c2 in excess of 28.5 T is about 2 T larger than that of the so-called RHQT Nb₃Al. Large Al-Ge filament size in the precursors over a few microns might be acceptable to improve high-field J_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.