Quaternary phases with Fe₂P-type structure in R-Ag-Al-Ge systems (R = Pr, Sm)

Chem. Met. Alloys 3 (2010) 53-61

https://doi.org/10.30970/cma3.0173

Roksolana KOZAK, Oksana ZAHARKO, Antonio CERVELLINO, Lev AKSELRUD, Roman GLADYSHEVSKII

The existence of limited solid solutions based on the ternary compounds PrAg_1.40‑1.20Ge_0.60‑0.80 and SmAg_1.40‑0.98Ge_0.60‑1.02 with Fe₂P-type structure (hP9, P-62m), was established at 33.3 at.% R in the quaternary systems R–Ag–Al–Ge (R = Pr, Sm) at 873 K. The crystal structures of the solid solutions were determined from conventional X-ray (a = 0.7232(1), c = 0.44081(8) nm for the composition PrAg_0.90Al_0.35Ge_0.75 and a = 0.71180(5), c = 0.43634(5) nm for SmAg_0.90Al_0.39Ge_0.71) and synchrotron (a = 0.72311(2), c = 0.44101(2) nm for PrAg_0.87Al_0.38Ge_0.75) powder diffraction data. A statistical mixture of Ag and Al atoms occupy the 3g site and forms columns of trigonal prisms with Ge atoms at the center (1a site), whereas a statistical mixture of Ge and Ag atoms is situated at the centers of the trigonal prisms R₆ (2d site).

Atomic coordinates and isotropic displacement parameters for PrAg_0.87Al_0.38Ge_0.75 (Fe₂P, hP9, P-62m, a = 0.72311(2), c = 0.44101(2) nm, Z = 3).

Keywords

Rare-earth / Silver / Aluminum / Germanium / Solid solution / X-ray diffraction / Crystal structure