Synthesis and Characterization of Manganese-Rich Silicide (α-Mn₅Si₃, β-Mn₅Si₃, and β-Mn₃Si) Nanowires

The Mn–Si binary phase diagram contains seven distinct equilibrium phases; however, to date, only two phases have been reported in nanowire (NW) morphology. We report the simple reaction of Mn vapor with a Si substrate in a H 2 atmosphere to lead to the formation of NW mixtures of MnSi and three new NW phases α-Mn 5 Si 3, β-Mn 5 Si 3, and β-Mn 3 Si, with the more Mn-rich phases formed at progressively higher temperatures from 800 to 940 °C identified using electron diffraction, together with other structural characterization techniques. Furthermore, the observation of β-Mn 5 Si 3 NWs having the D 8 m W 5 Si 3 structure type, which is a structure never observed in the Mn–Si system, represents the first report of Mn 5 Si 3 polymorphism. The purposeful use of excess metal species and intentional limitation of vaporous Si species during NW synthesis has led to the first synthesis of manganese-rich silicide NWs.