Abstract:

Four different nominal compositions MgB2, Mg1.5B2, Mg2B2 and Mg2.5B2 were produced by excess Mg method and hot press. These superconducting samples were compared in terms of structural, electric and magnetic properties. The superconducting phase was determined by XRD analysis, which indicated the formation of MgB2 structure as a main matrix with some amount of non-superconducting phases, such as metallic Mg and minor amount of MgO. The electric properties of the samples were characterized by low temperature resistivity measurements under different magnetic fields 0.5, 1.0, 3.0 T. The results showed that the superconducting Tc,onset and Tc,offset transition temperatures moved to lower values. These results indicate that excess Mg method improves the superconducting and magnetic properties of MgB2, as well as enhanced the rigidity and ductility of the samples.  Experimental results showed the advantages of the proposed methods, established the most suitable transition temperature of the samples, as well as the decline from the superconducting to normal state.  

Keywords: