Thermoelectric properties of p-type Si-rich higher manganese silicide for mid-temperature applications

Sulfur Vacancy-Driven Band Splitting and Phonon Anharmonicity Enhance the Thermoelectric Performance in n-Type CuFeS2

“…It can be seen that the lattice parameters decrease with the increase in sulfur vacancies until x = 0.1, whereas the CuFeS 1.8 sample shows an incremental increase, probably due to the presence of the secondary phase Cu 17.6 Fe 17.6 S 32 (Talnakhite). From the profile fitting of Rietveld refinement using GSAS II software, the lattice parameters of the CuFeS 2−x samples (see Table 1) were obtained as a = 5.2892(0) Å and c = 10.4252(8) Å, a = 5.2870 (7) Å and c = 10.4250(5) Å, and a = 5.2909(4) Å and c = 10.4268(5) Å, for CuFeS 2 , CuFeS 1.9 , and CuFeS 1.8 , respectively, as seen in Figure 1d, and the Supporting Information, SI, Figure S1a,b. The Rietveld refinement also verifies the existence of a secondary phase of Cu 17.6 Fe 17.6 S 32 in a minor proportion in CuFeS 1.8 , as seen in Figure 1c, quantified to be 21.7 wt %.…”

“…Moreover, a high-performance TE material must possess a high σ, and a large S with low total thermal conductivity, κ total = κ el + κ latt , in order to yield a high zT . However, attaining a high zT is cumbersome because S , σ, and κ el are interdependent on the carrier concentration. − In this regard, numerous strategies have been implemented to increase the numerator part, power factor ( S 2 σ), such as the energy filtering of minority carriers, − creating resonant states around the Fermi level ( E F ), − and facilitating the convergence of valence subbands. − Alternatively, the thermal conductivity could also be effectively reduced by introducing nano/meso-precipitates, − grain boundary phonon scattering, − and intrinsic bond anharmonicity − in the state-of-the-art materials, such as Bi 2 Te 3 , , PbTe, , SnSe, , GeTe, , and have been recently promoted as highly efficient, cost-effective, and environmentally friendly TE materials belonging to classes, namely silicides, − skutterudites, , and antimonides. − On the other hand, high-performance TE materials comprise toxic, expensive, or scarce elements in their composition, which resulted in the hunt for alternate earth-abundant materials containing inexpensive elements, leading to the discovery of ternary and quaternary sulfides. While p -type sulfides show enhanced figure of merit, n- type equivalents, however, remain scarce.…”

Physics and technology of thermoelectric materials and devices

“…In many cases, the elements in stoichiometric ratio were induction melted in a boron nitride coated graphite crucible or boron nitride crucible followed by evacuating and filling with argon gas in a stainless steel made closed chamber, whereas in other cases, melting was carried out for stoichiometrically weighed elements sealed in noble gas filled/vacuumized, sealed quartz ampoule. For instance, alloys like Bi 2 Te 3 /Sb 2 Te 3 [480], Mg 2 Sn [483], higher manganese silicides (MnSiγ) [484], Mg 2 Si [485], Heuslers [486], half-Heuslers [487], (Ti,Zr,Hf)(Co,Ni)Sb-InSb nanocomposites [488], etc, were melted by loading the respective elements into graphite/boron nitride crucibles. Additionally, compounds such as CoSb 3 alloys [489], Mg 3 Sb 2 [490], PbTe/GeTe alloys [491], ZrNiSn half-Heusler alloys [492], etc, were synthesized by induction melting them at their appropriate melting temperatures in a vacuum sealed/inert gas filled quartz tubes.…”

Nanostructure Approach Enhancing the Thermoelectric Performance of a p-Type HMS-CrSi2 Composite Synthesized by the MS–SPS Technique

“…Due to the structural complexity and narrow composition existence in the binary manganese–silicon phase diagram, the synthesis of semiconducting p-type HMS is a peculiar and challenging task. ,, Moreover, the synthesis of HMS possesses excess Si/metallic MnSi, employing conventional synthesis techniques. , On the other hand, these excess phases are detrimental to thermoelectric properties, significantly affecting zT , which are unfavorable for commercial device applications. The engineering of a microstructure employing novel material processing techniques was reported in literary works to circumvent these issues. , Recent studies have shown that the introduction of high-density interfaces and grain boundaries using a nano/ultrafine grain structure enhances phonon scattering significantly. ,, This phonon scattering significantly reduces thermal conductivity without affecting the electrical conductivity, resulting in an improved zT .…”

“…3,20,21 Moreover, the synthesis of HMS possesses excess Si/metallic MnSi, employing conventional synthesis techniques. 14,22 On the other hand, these excess phases are detrimental to thermoelectric properties, significantly affecting zT, which are unfavorable for commercial device applications. The engineering of a microstructure employing novel material processing techniques was reported in literary works to circumvent these issues.…”