Investigation on superconducting and magnetic levitation force behaviour of excess Mg doped-bulk MgB2 superconductors

Abstract A series bulk samples of MgB 2 + x wt % of Mg (x = 0, 5, 10, 15, 20 and 30) were fabricated by solid state reaction method. The structural and electromagnetic properties of MgB 2 samples were studied by using X-ray diffraction (XRD), scanning electronic microscope (SEM), electrical resistivity (R-T), Magnetic hysteresis (M-H) and magnetic levitation force measurements. The maximum repulsive and attractive force values of 15 wt % of excess magnesium MgB 2 sample compared to the other samples imply that the intergranular connection between grains enhanced while pore and microcrack density decreased and this situation brings the increasing of the values of the radius of a shielding current loop (r) and the critical current density (J c ). Additionally, it was determined that to obtain the enhancement of the micro and macro structure properties, causing to the higher critical current density, and the maximum levitation and lateral force values, the optimum excess magnesium content was 15 wt % into sample. This results can be guide the researchers studying on the material-fabrication and the magnetic bearing system.