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

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 (T-sin), at which best performance in transport critical current density (J(c)) at 4.2 K in 10 T is obtained for the tapes, to about 600 degrees C. This temperature is lower than that by about 100 degrees C for the tapes using the milled powders without Sn addition. However, T-sin reduction brings about the decrease of critical temperature (T-c) as well. Nevertheless the addition of small amount of Sn does not cause J(c) deterioration at all and the J(c) value at 4.2 K and 10 T is around 200 A/mm(2). Although the J(c) property degrades with further decreasing the T-sin the corresponding value is still 100 A/mm(2) when sintered at 500 degrees C. The J(c) curves as a function of T-sin just shift to lower temperatures by about 100 degrees C by Sn addition. The anisotropy of the transport J(c) property with respect to the applied magnetic field direction is negligible, which is independent of Sn addition.