Synthesis, Crystal Structure, and Ru/Ir Site Preference in the Complex Boride Series Ti2FeRu5–xIrxB2 and Zr2Fe1–δRu5–x+δIrxB2 (x = 1–4, δ < 0.15)


  • In Memory of Professor Hans Georg von Schnering


Polycrystalline samples and single crystals of the complex boride series Ti2FeRu5–xIrxB2 and Zr2Fe1–δRu5–x+δIrxB2 (x = 1–4, δ < 0.15) were synthesized by arc melting the elements and characterized by powder and single-crystal X-ray diffraction as well as energy dispersive spectroscopy. All quinary phases could be synthesized in the titanium series, whereas only the first two ruthenium-rich phases are stable and both are always present in nearly all synthetic targets of the zirconium series. These compounds crystallize in the tetragonal space group P4/mbm (Z = 2) and they represent the first quinary substitutional variants of the Ti3Co5B2-type structure containing a mixture of 4d/5d transition metals. Their structures consist of layers of ruthenium and iridium atoms, building trigonal, tetragonal, and pentagonal prisms, in which the other elements are located. The trigonal prisms are filled with boron and the pentagonal prisms accommodate either titanium or zirconium. The tetragonal prisms are filled either with iron (in the Ti series) or with an iron-rich Fe/Ru mixture (in the Zr series). Ruthenium and iridium share two sites in these structures leading to a strong size-dependent site preference in both series.