RE10TCd3 (RE = Y, Tb - Tm, Lu; T = Fe, Co, Ni, Ru, Rh, Pd) - Rare Earth-rich Phases with Ordered anti-Co2Al5 Structure

The rare earth-rich intermetallic cadmium compounds RE10TCd3 (RE = Y, Tb -Tm, Lu; T = Fe, Co, Ni, Ru, Rh, Pd) were synthesized by induction melting of the elements in sealed niobium ampoules. These cadmium intermetallics crystallize with an ordered variant of the hexagonal Co2Al5 type, space group P6(3)/mmc. The three crystallographically independent rare earth atoms lie on the aluminum sites, while the transition metal and cadmium atoms are ordered on the two cobalt positions. The structures of Y10Co1.103Cd2.897, Y10NiCd3, Y10RuCd3, Y10PdCd3, Er9.92FeCd3.08, and Er9.82NiCd3.18 were refined from single-crystal X-ray diffraction data. Some of the crystals showed small degrees of RE/Cd, respectively T/Cd mixing. The striking structural building units are transition metal centered T@RE6 trigonal prisms (TP) that are condensed to empty RE6 octahedra (O), building infinite center dot center dot center dot TP-O-O center dot center dot center dot rows in c direction. The second motifs are slightly flattened RE3@Cd6RE16 icosahedra. The latter are condensed via common triangular faced along the c axis. Each center dot center dot center dot TP-O-O center dot center dot center dot row is enrolled by three rows of condensed RE3@Cd6RE16 icosahedra in the motif of a hexagonal rod packing.