Increased critical current density of in-situ MgB2 wires by Mg deficiency

• Preparation of mechanically alloyed powders with a wide variation of the Mg:B-ratio.
• Influence of this ratio on phase composition and on grain size of in bulk samples.
• Increase of irreversibility field for Mg deficient samples.
• Transport current density of wires is increasing considerably with Mg deficiency.

In this contribution the influence of the Mg:B-stoichiometry in the precursor on the structural and electrical properties of bulks and wires prepared with mechanically alloyed powder is discussed. The Mg to B ratio in the powder was varied in the range of x = 0.7 to 1.1 (MgxB2). Analysing the properties of bulks and wires prepared with such precursor powders it was found that Mg-deficiency can increase the amount of MgB2 phase, the MgB2 diffraction peak width, the irreversibility field and the critical current density considerably.