Synthesis, structure and properties of the new rare-earth Zintl phase Yb11GaSb9

A new rare-earth rich Zintl phase Yb11GaSb9 was synthesized by direct fusion of the corresponding elements, and large single crystals of the compound were obtained from high temperature flux synthesis. Its crystal structure was determined by single-crystal X-ray diffraction to be orthorhombic in the non-centrosymmetric space group Iba2 (No. 45), Z=4 (R1=3.24%, wR2=6.40%) with a=11.7257(12)Å, b=12.3204(13)Å, c=16.633(2)Å measured at 90(3) K. The structure belongs to the Ca11InSb9-type and can be viewed as built of isolated Sb4-tetrahedra centered by Ga, Sb-dimers and isolated Sb anions, which are separated by Yb2+ cations. Electron count according to the Zintl formalism suggests that the phase is electron-precise and charge-balanced, which is supported by the virtually temperature-independent magnetization for Yb11GaSb9. Electrical resistivity data from 2 to 400 K confirm that Yb11GaSb9 is a small band-gap semiconductor with room temperature resistivity ρ298=45.1mΩcm, and low-temperature resistivity at 2 K ρ2=1.9Ωcm. As such, Yb11GaSb9 and related compounds might be promising materials for thermoelectric applications, and currently, efforts to synthesize new members of this family and test their thermoelectric performance are under way.