Reduced sintering temperature in ex situ processed MgB2 tapes using filling powders with Sn addition

Abstract

Ex situ processed tapes using ball milled MgB2 powders with Sn addition were sintered at various temperatures. Sn addition causes the formation of some amorphous or poor crystalline phase in the as-milled powders and reduces the optimal sintering temperature (Tsin), at which best performance in transport critical current density (Jc) at 4.2 K in 10 T is obtained for the tapes, to about 600 °C. This temperature is lower than that by about 100 °C for the tapes using the milled powders without Sn addition. However, Tsin reduction brings about the decrease of critical temperature (Tc) as well. Nevertheless the addition of small amount of Sn does not cause Jc deterioration at all and the Jc value at 4.2 K and 10 T is around 200 A/mm2. Although the Jc property degrades with further decreasing the Tsin, the corresponding value is still 100 A/mm2 when sintered at 500 °C. The Jc curves as a function of Tsin just shift to lower temperatures by about 100 °C by Sn addition. The anisotropy of the transport Jc property with respect to the applied magnetic field direction is negligible, which is independent of Sn addition.