Formation of a series of chimney–ladder compounds in the Ru–Re–Si system

Rhenium-alloyed ruthenium sesquisilicide alloys have been prepared over the wide composition range Ru1−δReδSi1.5, 0 ⩽ δ ⩽ 0.85. The phase relationships of these alloys have been investigated using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Alloys with δ ⩾ 0.03 are multi-phase, composed of a series of (Ru,Re)Siy chimney–ladder phases with compositions of Ru1−xRexSi1.5386+0.1783x (0.14 ⩽ x ⩽ 0.76) and B20-type monosilicide (Ru,Re)Si as a secondary phase. These chimney–ladder structures are considered to form to stabilize the high-temperature Ru2Si3 chimney–ladder phase through the substitution of Ru with Re. The solubility limit of Re in a series of chimney–ladder phases is as large as 76% Re (x = 0.76) and the Si/(Ru + Re) ratio of the chimney–ladder phases increases with increasing Re content. The observed deviation of the chimney–ladder structure from the idealized composition and the possibility of adjusting the semiconducting properties of these chimney–ladder structures are discussed in terms of the valence electron concentration per metal atom.