抄録
Superconducting Nb3Al tapes with Nb sheath were prepared by the powder metallurgy method using the diffusion reaction between σ-phase (Nb2Al) and Nb powders. External heating using an electric furnace and ohmic heating by electrifying the tape specimens were compared to obtain the stoichiometric composition of A15 Nb3Al. During ohmic heating, control of the ultimate temperature was enabled by measuring the radiant temperature on the surface of the tapes. In the reaction between σ-phase and Nb powders, the reaction temperature, above which only the A15 phase is produced, was lowered by 100-200°C as compared with the reaction between Al and Nb powders. For the specimen obtained by ohmic heating and subsequent annealing, the highest onset Tc was 18.5K. Jc was 41A/mm2 at 20T and Bc2 was 27T. For the specimen prepared by ohmic heating, Tc increased by 2.0K after post annealing at 800°C for 10h.
