R_2-xTi_3+xGe₄ compounds in the R–Ti–Ge (R = Gd-Lu) systems

Chem. Met. Alloys 11 (2018) 14-17

https://doi.org/10.30970/cma11.0378

Bogdana BACHYNSKA, Nataliya MUTS, Khrystyna MILIYANCHUK, Roman GLADYSHEVSKII

The existence of five R_2-xTi_3+xGe₄ compounds (R = Gd, Tb, Dy, Ho, Er) was confirmed at 600°C and two new compounds, Tm_1.79(2)Ti_3.21(2)Ge₄ and Lu_1.74(2)Ti_3.26(2)Ge₄, were found. No ~R₂Ti₃Ge₄ compound was observed for Yb. All the compounds crystallize with partly ordered variants of the structure type Sm₅Ge₄ (Pearson symbol oP36, space group Pnma). On going from gadolinium to lutetium, the unit-cell parameters are reduced, due to the lanthanide contraction, but also due to the fact that the refined composition becomes richer in Ti. One of the metal-atom sites located between the structural slabs was found to be fully occupied by titanium, whereas the other one is mainly or fully occupied by the rare-earth metal. The site located inside the slabs (rhombic dodecahedral coordination) is preferentially occupied by Ti.

Rhombic dodecahedron surrounding site M3 in the R_2-xTi_3+xGe₄ compounds.

Keywords

Rare-earth metals / Titanium / Germanides / Crystal structure