R2-xTi3+xGe4 compounds in the RTiGe (R = Gd-Lu) systems

 

Chem. Met. Alloys 11 (2018) 14-17

 

Bogdana BACHYNSKA, Nataliya MUTS, Khrystyna MILIYANCHUK, Roman GLADYSHEVSKII

 

The existence of five R2-xTi3+xGe4 compounds (R = Gd, Tb, Dy, Ho, Er) was confirmed at 600C and two new compounds, Tm1.79(2)Ti3.21(2)Ge4 and Lu1.74(2)Ti3.26(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 R2-xTi3+xGe4 compounds.

 

Keywords

Rare-earth metals / Titanium / Germanides / Crystal structure