Enhancement of mechanical and superconducting properties of MgB₂

We demonstrate the higher mechanical strength and density and superconducting properties of MgB₂ compounds by controlling the initial mixing ratio of Mg and B in a Ta tube. It is found that the extra Mg as a starting element in a sealed Ta tube establishes a good environment for the formation of MgB₂ with a large grain size of 9-16 μm diam, rather than existing as an impurity. As a result, MgB₂, which was synthesized from mixing a ratio of Mg:B=1.3:2, shows much higher mechanical strength and density. In addition, electrical and superconducting properties are also enhanced for application, which indicates a more effective interconnection between grains. The critical current density is increased almost by two times compared with the compound, synthesized from the stoichiometric starting elements, which is important for the application of MgB₂.