Thermally induced substitutional reaction of Fe into Mo₂GaC thin films

The first Fe-based MAX phase is realized by solid-state substitution reaction of an Fe/Au/Mo2GaC thin-film diffusion couple, as determined by X-ray diffraction and scanning transmission electron microscopy. Chemical analysis together with elemental mapping reveals that as much as 50 at.% Fe on the A site can be obtained by thermally induced Au and Fe substitution for Ga atomic layers in Mo2GaC. One-sixth of the original Ga is also replaced by Au atoms. When annealing Mo2GaC thin films covered with Fe only, the Mo2GaC phase remains intact, that is, Au acts as a catalyst for the substitution reaction.IMPACT STATEMENT The first direct evidence showing Fe-containing MAX phase, Mo2AC, with Fe ∼50 at.% on the A sites is presented, synthesized by thermally induced Fe and Au substitution reaction catalyzed by Au.