Possibility of the Higher Critical Temperature on MgB2 Superconductor Synthesized by Powder-In-Sealed-Tube Method

MgB2 is a metal compound superconductor which has critical temperature value ~ 39 K. The critical temperature of MgB2 superconducting wire is higher than Nb-based superconductor, NbTi and Nb3Sn. It is a promising superconductor to replace the Nb-based superconductor that has been applied as a widely used superconducting wire. The aim of this study is to synthesize MgB2 superconductor with the various amount of Mg element using powder-in-sealed-tube method. Mg and B powders were mixed, grounded and poured into stainless steel SS304 tube. As-mixed powder was then heated at 800  C for 2 h in standard air ambient inside a sealed tube. After that, the crystal structures, surface morphology and resistivity versus temperature of all samples were characterized using X-ray diffraction (XRD), scanning electron microscopy and cryogenic system, respectively. Based on the result of XRD, the majority of MgB2 phase was formed even though there were slightly small amount of B2O phases. The critical temperature (Tc) onset of MgB2 with the addition of 0, − 5, − 10, 5 and 10 wt% Mg was calculated 42.03; 42.25; 42; and 41.8 K, accordingly. These critical temperature values are relatively higher than other studies among this type of superconductors. And then, to study the grinding effect, one of the as-calcined pellets was ground and pressed to form bulk sample again. TC,onset and TC,zero of this sample were decreased 3 and 18 K, respectively.