The systems Sr–Zn–{Si,Ge}: Phase equilibria and crystal structure of ternary phases

Phase relations have been established by electron probe microanalysis (EPMA) and X-ray powder diffraction (XPD) for the Sr-poor part of the ternary systems Sr–Zn–Si at 800 °C and Sr–Zn–Ge at 700 °C. In the Sr–Zn–Si system one new ternary compound SrZn 2+ x Si 2− x (0≤ x ≤0.45) with CeAl 2 Ga 2 structure and a statistical mixture of Zn/Si in the 4 e site was found. Neither a type-I nor a type-IX clathrate phase was encountered. This system is characterized by formation of two further phases, i.e. SrZn 1− x Si 1+ x with ZrBeSi-type (0.16≤ x ≤0.22) and SrZn 1− x Si 1+ x with AlB 2 -type (0.35≤ x ≤0.65) with a random distribution of Zn/Si atoms in the 2 c site. For the Sr–Zn–Ge system, the homogeneity regions of the isotypic phases SrZn 1− x Ge 1+ x with ZrBeSi-type (0≤ x ≤0.17) and AlB 2 -type (0.32≤ x ≤0.56), respectively, have been determined. Whereas the germanide SrZn 2+ x Ge 2− x (CeAl 2 Ga 2 -type) is characterized by a homogeneity region (0≤ x ≤0.5), the clathrate type-I phase Sr 8 Zn 8 Ge 38 shows a point composition.