Determination of the solubility range and crystal structure of the Mg-rich ternary compound in the Ca–Mg–Zn system

The homogeneity range and crystal structure of the Mg-rich ternary solid solution has been determined using SEM, EPMA/WDS, TEM and X-ray diffraction. This compound has the Ca3MgxZn15−x (4.6 ≤ x ≤ 12) formula at 335 °C. The refinement of the XRD patterns was carried out by Rietveld analysis, XRD data has shown that this solid solution crystallizes in hexagonal structure having P63/mmc (194) space group and Sc3Ni11Si4 prototype. The lattice parameters decrease linearly with decreasing Mg content obeying Vegard’s law. The fractional atomic occupancy of 6h, 4f, 2b and 12k sites of this compound are function of Mg concentration. Focused Ion Beam has been used to lift TEM specimen of the ternary compound and the hexagonal structure has been confirmed by means of selected area electron diffraction data. Based on the atomic occupancy results and the crystallographic details, a three sublattice (Ca)(Zn)(Mg, Zn)4 model is proposed for this compound.