Low temperature formation of superconducting MgB₂ phase from elements by mechanical milling

The influence of the mechanical milling of the corresponding powder elements on the formation of superconducting MgB₂ phase was investigated. Mg and B powders were attrition-milled, and then the milled powder mixture was annealed under atmospheric pressure of argon. MgB₂ phase clearly appeared after annealing the 60 min milled powder mixture at 500 °C. This powder mixture showed much larger diamagnetism magnitude at 4 K than that was milled for 5 min. The structural analyses revealed that the superconducting phase in this powder was formed at the Mg and B composite structure which was fabricated by the longer mechanical milling. These results indicate that the mechanical milling of the powder elements can enhance the reactivity for the formation of MgB₂.