Determine the Fe solubility limit in MgB2

Ascertain the solubility limit x of iron substitution on the magnesium site in MgB2 by determining the maximum concentration for which single-phase Mg1−xFexB2 can be achieved under realistic synthesis conditions.

Background

The extent to which iron can be incorporated into the MgB2 lattice has been debated, with prior reports on polycrystalline materials claiming high nominal solubility (up to x = 0.4) but showing inconsistent trends in lattice parameters and critical temperature. Such inconsistencies suggest partial incorporation of Fe and formation of iron-boride impurity phases, casting doubt on the true substitution limit.

Establishing the actual solubility limit is crucial for both fundamental understanding of how transition-metal substitution affects the two-gap superconductivity in MgB2 and for practical considerations in Fe-clad wire fabrication, where possible Fe diffusion into MgB2 during processing could influence performance.