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

Energetic evaluation of the semiconducting mono-, sesqui-, and di-silicides of the 8th group elements (Fe, Ru and Os) using first-principle calculations

“…They are shown in Fig. 1. 1 Cerius 2 is a trademark of Accelrys, Inc. 2 As the reference state of iron, we used bcc iron in nonmagnetic state. We thought that the present method is not appropriate to estimate the formation energy with a magnetic phase as a reference state since the pseudopotential scheme is known to overestimates the magnetic moment and the magnetic energy (DE, the energy difference between the nonmagnetic and ferromagnetic phases).…”

“…Ru 2 Si 3 crystallizes into two different types of structures, the orthorhombic Ru 2 Si 3 -type structure with the space group of Pbcn at low temperature (a-Ru 2 Si 3 ) and the tetragonal Ru 2 Sn 3 -type structure with the space group of P4c2 at high temperature (b-Ru 2 Si 3 ). The b-Ru 2 Si 3 phase is a member of the class of compounds referred to as the chimney-ladder phases but the distortion of the Si positions on cooling destroys the tetragonal symmetry, resulting in two unit cells of the b structure transforming to one unit cell of the a-structure [2]. The target of the present study is the compound with a-Ru 2 Si 3 -type structure, the unit cell of which is composed of 16 Ru atoms and 24 Si atoms.…”

Structural and Thermoelectric Properties of Chimney–Ladder Compounds in the Ru-Mn-Si System

“…EDS analysis in a SEM reveals that the contrast variation corresponds to compositional variation in the (Ru,Mn)Si y sesquisilicide phase, as observed previously for chimney-ladder phases in the RuRe-Si ternary system. [11][12][13] Thus, a range of composition is indicated for the (Ru,Mn)Si y sesquisilicide phase in the ternary phase diagram of Fig. 1e for the Ru 1Àx Mn x Si 1.5 alloys.…”

“…1,9,10 We recently found that substitution of Ru (group 8) in Ru 2 Si 3 by Re (group 7) stabilizes the HT phase with the chimney-ladder structure to appear at low temperatures, so that a series of chimney-ladder phases Ru 1Àx Re x Si y are formed over a wide composition range between Ru 2 Si 3 and Re 4 Si 7 . 11,12 It is interesting to note that the Si/M values for these chimney-ladder phases increase with increased Re content, so that the valence electron count (VEC) per M atom in the compounds is maintained (VEC = 14). 13 In the present study, we investigated the phase relationships and crystal structures in Mn-substituted ruthenium sesquisilicide alloys by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).…”

“…1 Some of the family of compounds with the chimney-ladder structures, including high manganese silicides (Mn 4 Si 7 , Mn 11 Si 19 , Mn 15 Si 26 , and so forth [2][3][4], are known to exhibit a high Seebeck coefficient and low thermal conductivity. The chimney-ladder compounds have been investigated as candidate thermoelectric materials, [5][6][7][8] because thermoelectric performance is evaluated by the dimensionless figure of merit ZT = a 2 T/(qk), where a, q, k, and T are the Seebeck coefficient, electrical resistivity, thermal conductivity, and temperature, respectively.…”