Synthesis and structural characterization of dense polycrystalline Mg9Sn5, a metastable Mg-Sn phase

We present a method for synthesizing bulk dense polycrystalline Mg9Sn5, a phase that is related to the familiar Mg2Sn phase but is metastable at ambient pressure and temperature. Our procedure requires significantly lower temperatures and pressures, which are in the 100 MPa range compared to the previously reported methods that required pressures in the GPa range. We used a combination of high energy ball milling and current activated pressure assisted densification (CAPAD) to synthesize and retain the high pressure phase in a bulk (low porosity) form. We show the effect of CAPAD processing temperature and pressure on the density and phase composition of the material. We also present the first neutron diffraction study to confirm phase identity and refine the structure of Mg9Sn5.