Jc increase of MPMG-processed YBa2Cu3O7−x (Y-123) bulk due to fast neutron irradiation

The change in pinning properties of YBa2Cu3O7−x (Y-123) prepared by MPMG process due to fast neutron irradiation and thermal annealing treatment was investigated in order to confirm that fast neutron irradiation is effective for the Jc increase in practical material as well as single crystal. In this study, MPMG-processed Y-123 specimens (1.5 mm × 1.0 mm × 0.5 mm) with 0.5 wt% of Pt were irradiated with fast neutrons from 2.9 × 1015 cm−2 to 8.0 × 1018 cm−2 below 313 K. Before and after the fast neutron irradiation, Jc was evaluated from the magnetic hysteresis loop at 20 K, 40 K and 60 K using the extended Bean's model, and pinning potential was obtained from the magnetic relaxation curve at 20 K. In addition, Tc was evaluated by AC magnetization measurement. The maximum values of Jc were 1200 kA cm−2 at 20 K and 7 T, and 400 kA cm−2 at 40 K and 7 T. They exceeded the target value for its practical superconducting magnet uses e.g. nuclear fusion reactor, magnetic levitation, etc. Furthermore, Tc was recovered sufficiently by the thermal annealing treatment. It turns out that the pinning centers introduced by neutron irradiation work effectively also in the practical material which has already included the strong pinning centers of dispersed Y-211 phase.