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

Abstract

Significant variations in figure-of-merit (zT) values between n and p-type silicides impede the thermoelectric performance of cost-effective silicide-based thermoelectric power generators (TEGs). We report a significantly enhanced and compatible zT value in a p-type higher manganese silicide (HMS)-CrSi 2 nanocomposite synthesized using a combination of liquid-phase melt-spinning (MS) and solid-phase spark plasma sintering (SPS). The MS−SPS-processed HMS-CrSi 2 (80−20 wt %) composite material shows substantially enhanced electrical conductivity and a high power factor value. Also, a remarkable enhancement of the HMS-20 wt % CrSi 2 composite materials' zT ≃ 0.92 is realized due to a concurrent reduction in its thermal conductivity (κ). This 2-fold increase in the zT value compared to pure HMS exhibited by the composite material, consisting of nanoscale dimensional grain features, mainly originates from a rapid solidification melt-spinning process. The composite of HMS-CrSi 2 synthesized using the combination of MS and SPS techniques is investigated to realize a high thermoelectric figure-of-merit (zT) value in a p-type thermoelectric material, which is considered a potential compatible counterpart for n-type silicides.

Physics and technology of thermoelectric materials and devices

“…In a recent work by Prajapati et al a zT of 0.92 have achieved at 873 K for melt spun HMS-20% CrSi 2 composites. It is noteworthy that the combined participation of composite and nanostructures with the grain size ranged from 100 to 300 nm facilated high figure of merit in this case [29].…”

“…Particularly, many strategies have been proposed to enhance the power factor by modifying the electronic structures, such as (a) doping and/or alloying [21], (b) minority energy carrier filtering [24], (c) deep-level or resonant states formation [25] and (d) conduction/valence sub-band convergence [26]. It is also imperative to reduce the lattice thermal conductivity via phonon scattering through (i) doping/alloying for low-wavelength phonon scattering by massfluctuation scattering [27], (ii) nano-structuring/embedding the nanostructured particles in the host matrix/formation of interfaces for mid-wavelength phonons scattering [28], and (iii) micro/nano-composites for long-wavelength phonon scattering [29]. In this review, we have provided the recent highlight of various physical concepts employed in the thermoelectric research.…”

“…In addition to that, through melt spinning, homogeneity of the composition can be retained along with the production of multi-scale nanostructures [515]. Most importantly, the heirarchical nanostructures with the grain size in the range of 100-800 nm of melt-spun ribbons scatters more mid-to-long wavelength phonons thereby reducing the thermal conductivity many folds without disturbing the electrical conductivity [29].…”

Enhancement in Thermoelectric Performance in Ti-doped Yb0.4Co4Sb12 Skutterudites via Carrier Optimization and Phonon Anharmonicity

“…Nevertheless, the interdependency of TE parameters of σ, S , and κ total prevents the decoupling of the former and latter terms. However, many strategic efforts have been made such as band convergence, electron filtering, nanocomposites, modulation doping, multiscale precipitation, and anharmonicity, which led to successful enhancement in S 2 σ and lowering the thermal conductivity successfully. In this context, though the state-of-the-art materials, namely, Bi 2 Te 3 , − PbTe, ,, PbSe, , GeTe, , SnSe, , SnTe, and half-Heusler, have been known for their superior thermoelectric performance within the operating temperature range, most of them could not be used for large-scale applications because of the costly and toxic constituent elements.…”

High-Performance Functionalized Mg2Si0.9Sn0.1 Thermoelectric Leg Synthesis by a Single-Step Reactive SPS Process

“…However, the presently used high zT materials like Bi 2 Te 3 , PbTe, and SiGe are either highly toxic or expensive. The low-cost, earth-abundant, and nontoxic silicide-based materials, such as Mg 2 Si 1– x Sn x , MnSi 2– x , and FeSi 2 , were studied to circumvent these issues. − Most of the previously published works on cost-effective silicon-based materials have reported high zT values; however, limited demonstrations of their device applications have been made thus far. The integration of low-cost Mg 2 Si 1– x Sn x materials in TEGs is mainly restricted by one of the leading issues, the electrical contact resistance between thermoelectric elements and contact electrodes.…”