Effect of W-addition on pinning property of MgB2

The W was added into the MgB2 superconductor. The Mg, B and W were sintered at 1173 K for 30 min under H2/Ar atmosphere. The W concentration x ranged from 0 to 0.05. The critical current Jc was analyzed by the extended critical state model. The enhancement of Jc became maximum for the x = 0.02 sample. The 5d transition metal W was added into the MgB2 superconductor. The Mg, B and W were sintered at 1173 K for 30 min under H2/Ar atmosphere in the electric furnace. The Wx(MgB2)1-x samples were prepared in the W concentration range of 0 ≤ x ≤ 0.05. Temperature and field dependences of magnetization were measured by the SQUID magneto-meter. The field and x dependences of Jc at 20 K were analyzed by the extended critical state model. The enhancement of Jc became maximum for the x = 0.02 sample.