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 Ru_1-δRe_δSi_1.5, 0 {less-than or slanted equal to} δ {less-than or slanted equal to} 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 {greater than or slanted equal to} 0.03 are multi-phase, composed of a series of (Ru,Re)Si_y chimney-ladder phases with compositions of Ru_1-xRe_xSi_{1.5386+0.1783x} (0.14 {less-than or slanted equal to} x {less-than or slanted equal to} 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.