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

Abstract

Directionally solidified alloys in the Ru-Mn-Si system exhibit a particular microstructure including columnar compositional variation due to the formation of many different chimneyladder phases along the growth direction. Despite the existence of the compositional variation, the crystal orientations of the neighboring chimney-ladder phases are preserved. Over the compositional interfaces, the metal sublattice is considered to be continuous while the Si sublattice is not. Heat treatment of the directionally solidified alloy with the nominal composition of Ru 0.10 Mn 0.90 Si 1.732 at 1100°C coarsens the compositional domains so as to reduce the density of the compositional interfaces. The values of the thermal conductivity increase with the decrease in the density of the compositional interfaces whereas those of the Seebeck coefficient and electrical resistivity are almost unchanged after the heat treatment. It is considered that the thermoelectric properties of the chimney-ladder compounds in the Ru-Mn-Si system can be enhanced by introducing a high density of the compositional interfaces.

Significant Enhancement of the Thermoelectric Performance of Higher Manganese Silicide by Incorporating MnTe Nanophase Derived from Te Nanowire

“…These values are even higher than those of pure HMS (1.60 × 10 −3 Wm −1 K −2 ) as well as those reported in state-of-the-art publications. 18,22,29,32 Moreover, the relatively uniform nano/bulk structure may also affect κ tot . Although Te NWs were used in the sample with n-hexane as solvent, κ tot seems a little higher than that MnSi 1.746 Te 0.03 specimen using Te powder, and the Te nanowire agglomerations may contribute a relatively weak nanometer size effect to the phonon scattering.…”

“…In contrast, because of the ultranarrow homogeneity range of HMS, two side phases, semimetallic MnSi and monatomic Si easily appeared in the HMS matrix. Specifically, the MnSi impurity phase is very difficult to be removed due to the relatively low formation enthalpy and the excellent chemical stability when HMS is fabricated via mechanical alloying, 22,43,44 arc melting, 32,36,45 solid-state reaction, 46 melt spinning, 29 and chemical vapor deposition. 30 Thus, to avoid the formation of second phases, the facile, rapid, and energy-saved avenue of wet ball milling, combined with SPS, was used to prepare pure HMS.…”

Energy harvesting: an integrated view of materials, devices and applications

“…Magnesium silicide (Mg 2 Si) has been reported to be a candidate as a thermoelectric material, particularly for temperatures ranging from 500 to 800 K. This thermoelectric material operates in a similar conversion temperature range to PbTe, TAGS (Ge-Te-Ag-Sb) and CoSb 3 , and is particularly interesting since it is one of the most abundant compounds on earth and its by-products are nontoxic [42]. The thermoelectric properties may also be improved in other silicides, such as the chimney-ladder compounds in the Ru-Mn-Si system, by introducing a high-density compositional interface [18,43].…”

“…Yb 14 MnSb 11 is an excellent material for high-temperature thermoelectrics, with a reported ZT of 1.0 at 1223 K and up to 1.3 with optimized alloying. Nowotny chimney-ladder [18,43] (NCL) compounds (figure 11(b)) are another class of complex crystal structure materials showing promise as PGECs. They have a variable length, columnar sublattice of non-metal atoms (ladders) residing in the channels (chimneys) of a metal atom sublattice, forming homologous families of complex structures with variable unit cell length or incommensurate crystal structures.…”