New processing technique for forming flexible A-15 superconducting tapes with extremely high critical current densities and magnetic fields

Alloys of Nb73Al12Si14.5B0.5 were rapidly quenched using the melt spinning technique to form fine amorphous ribbons. These were then annealed into A-15 tapes with a variety of grain sizes. The smaller the grain was the more flexible the tape and the higher the critical current density Jc. The best results were obtained for a tape with a grain size of 15 nm; it could be bent to a diameter of 1 mm without breaking and it had a Jc of 3.3×1010 A/m2 at a magnetic field of 20 T.