The effect of the Ag addition on FeSe superconducting wire by the ex-situ PIT method

We investigated the effect of an Ag addition to the FeSe 0.94 superconducting wire. Production and characterization of the Ag-added FeSe 0.94 superconducting wire were produced by the ex-situ PIT technique with an iron tube. The structural analysis (XRD and SEM) of the Ag-added FeSe 0.94 wire indicate that it is mainly composed of the tetragonal phase (β-FeSe) with a minor hexagonal (δ-FeSe) and cubic (α-Fe) secondary phases. The Ag spread inhomogeneous in the reacted layer, suggesting that it supports the intergrain connections. Moreover, a small amount of Ag entered into the crystal structure. The resistivity started to decrease at 10.5 K, and the zero-resistivity observed at 7.2 K was 0 T. The J c was calculated to be 80.7 A/cm 2 at 4.2 K in self-field. The presence of a non-superconducting binary phase of FeSe may behave as a pinning force promoting a larger critical current density. The upper critical field was estimated to be 66.3 T from linear exploration.