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Thermoelectric Peltier coolers (PCs) are being increasingly used as temperature stabilizers for optoelectronic devices. Increasing integration drives PC miniaturization, requiring thermoelectric materials with good strength. We demonstrate a simultaneous gain of thermoelectric and mechanical performance in (Bi, Sb)2Te3, and successfully fabricate micro PCs (2 × 2 mm2 cross-section) that show excellent maximum cooling temperature difference of 89.3 K with a hot-side temperature of 348 K. A multi-step process involving annealing, hot-forging and composition design, is developed to modify the atomic defects and nano- and microstructures. The peak ZT is improved to ∼1.50 at 348 K, and the flexural and compressive strengths are significantly enhanced to ∼140 MPa and ∼224 MPa, respectively. These achievements hold great potential for advancing solid-state refrigeration technology in small spaces. [ABSTRACT FROM AUTHOR]

Degenerate semiconductors usually demonstrate a metallic‐like conduction behavior, showing limited carrier mobility at high temperatures. Herein, by incorporating B4C nanoparticles into the Cu1.99Se system, an unusual switch from the "degenerate" to "non‐degenerate" semiconducting behavior is revealed as a result of the engineered interfaces. Heterogeneous interfaces and disordered Cu2Se amorphous phases are introduced in the Cu1.99Se/B4C composites, which generate a trapping effect against the mobile Cu ions, leading to a distinctive "hump" signature for electrical conductivity. Benefiting from this rare high‐temperature thermoelectric response, a high power factor is obtained due to reduced carrier concentration and enhanced mobility, and low lattice thermal conductivity is retained because of relatively stronger anharmonic lattice vibrations. Consequently, the Cu1.99Se + 0.9 vol.% B4C sample at least achieves a maximum thermoelectric figure of merit (ZT) of 2.6 at 1025 K with synergistically enhanced mechanical robustness. The present interface engineering strategy may be applicable to other thermoelectric materials with ionic migration characteristics. [ABSTRACT FROM AUTHOR]

GeTe and (Bi,Sb)2Te3 are two representative thermoelectric (TE) materials showing maximum performance at middle and low temperature, respectively. In order to achieve higher performance over the whole temperature range, their segmented one‐leg TE modules are designed and fabricated by one‐step spark plasma sintering (SPS). To search for contact and connect layers, the diffusion behavior of Fe, Ni, Cu, and Ti metal layers in GeTe is studied systematically. The results show that Ti with a similar linear expansivity (10.80 × 10−6 K−1) to GeTe, has low contact resistance (3 µΩ cm2) and thin diffusion layer (0.4 µm), and thus is an effective metallization layer for GeTe. The geometric structure of the GeTe/(Bi,Sb)2Te3 segmented one‐leg TE module and the ratio of GeTe to (Bi,Sb)2Te3 are determined by finite element simulation method. When the GeTe height ratio is 0.66, its theoretical maximum conversion efficiency (ηmax) can reach 15.9% without considering the thermal radiation and thermal/electrical contact resistance. The fabricated GeTe/(Bi,Sb)2Te3 segmented one‐leg TE module showed a ηmax up to 9.5% with a power density ≈ 7.45 mW mm−2, which are relatively high but lower than theoretical predictions, indicating that developing segmented TE modules is an effective approach to enhance TE conversion efficiency. [ABSTRACT FROM AUTHOR]

GeTe has attracted extensive interest due to its promising mid-temperature thermoelectric performance, yet the high cost and ferroelectric phase transformation may limit its application. Here, we explore the thermoelectric properties of electron doped GeMnTe2, which is a much cheaper derivative of GeTe with a rock-salt structure and a high thermoelectric figure of merit (ZT value) of 1.4. It is substantiated that an all-scale hierarchical structure including point defects at the atomic scale, endotaxially embedded nano-inclusions and precipitates are responsible for the strong scattering of phonons and low lattice thermal conductivity. Further synergistic modulation of electrical and thermal transport properties is successfully realized by Pb doping, which is effective in optimizing the carrier concentration and suppressing the phonon propagation by lattice softening and enhanced point defect scattering. The present work revealed the potential of GeMnTe2 as a promising candidate for mid-temperature thermoelectric materials and demonstrated the effectiveness of nanostructuring to enhance the thermoelectric performance. [ABSTRACT FROM AUTHOR]

Cu-based chalcogenides have attracted increasing attention as a potential thermoelectric material due to their unique structural features, high element abundance, and low toxicity. In this paper, a series of Cu1.8SbxSnyS compositions (0.01 ＜ x ＜ 0.04, 0.015 ＜ y ＜ 0.045) were prepared by a simple method combining mechanical alloying (MA) and spark plasma sintering (SPS). The results demonstrate that Sb/Sn co-doping can optimize the hole concentration and substantially improve the dimensionless figure of merit (ZT) of copper–sulfide Cu1.8S. The highest ZT, up to 1.2 at 773 K, was realized for the Cu1.8Sb0.02Sn0.03S sample and maintained a high power factor of 975 μW m−1 K−2. The reduction in thermal conductivity was linked to the heterogeneous phase of Cu12Sb4S13 and Cu4SnS4. Remarkably, after four testing cycles, the variation in ZT was less than 2%, indicating a good stability of the Sb/Sn co-doped Cu1.8S materials. [ABSTRACT FROM AUTHOR]

Pores in a solid can effectively reduce thermal conduction, but they are not favored in thermoelectric materials due to simultaneous deterioration of electrical conductivity. Conceivably, creating a porous structure may endow thermoelectric performance enhancement provided that overwhelming reduction of electrical conductivity can be suppressed. This work demonstrates such an example, in which a porous structure is formed leading to a significant enhancement in the thermoelectric figure of merit (zT). By a unique BiI 3 sublimation technique, pore networks can be introduced into tetrahedrite Cu 12 Sb 4 S 13 -based materials, accompanied by changes in their hierarchical structures. The addition of a small quantity of BiI 3 (0.7 vol%) results in a ≈72% reduction in the lattice thermal conductivity, whereas the electrical conductivity is improved due to unexpected enhanced carrier mobility. As a result, an enhanced zT of 1.15 at 723 K in porous tetrahedrite and a high conversion efficiency of 6% at ΔT = 419 K in a fabricated segmented single-leg based on this porous material are achieved. This work offers an effective way to concurrently modulate the electrical and thermal properties during the synthesis of high-performance porous thermoelectric materials., (© 2021 Wiley-VCH GmbH.)

Nanostructuring and defect engineering are increasingly employed as processing strategies for thermoelectric performance enhancement, and special attention has been paid to nanostructured interfaces and dislocations that can effectively scatter low- and mid-frequency phonons. This work demonstrated that their combination was realized in Fe 2 O 3 -dispersed tetrahedrite (Cu 12 Sb 4 S 13 ) nanocomposites, leading to significantly reduced thermal conductivities around 0.9 W m -1 K -1 at all temperatures and hence a high ZT value of ∼1.0, which increases by ∼33% compared with that of the matrix. The plausible enhancement mechanisms have been analyzed with an emphasis on the incorporation of magnetic γ-Fe 2 O 3 nanoparticles (NPs) into Cu 11.5 Ni 0.5 Sb 4 S 13 , leading to various nanostructures (NPs, nanoprecipitates, and nanotwins) and dislocations. A calculated efficiency of ∼9.3% and an average ZT of 0.63 also reveal the potential application of tetrahedrite at medium temperatures. Additionally, the mechanical properties are improved because of a second phase strengthening and nanotwin structures.

Bi 2 Te 3 -based compounds are the most mature and widely used thermoelectric materials. However, industrial device fabrication will inevitably produce a lot of Bi 2 Te 3 scraps, which results in wastes of expensive material resources. In this work, we recycled p -type (Bi,Sb) 2 Te 3 scraps and reprocessed them by making nanocomposites with nano-SiC. The thermoelectric performance was enhanced, and a high ZT value of 1.07 was achieved, which is a significant improvement compared with commercial p -type (Bi,Sb) 2 Te 3 ingots. Also, the hardness showed a notable increase, which is beneficial for device fabrication. In addition, we adjusted the proportion of Bi/Te of the commercial p -type (Bi,Sb) 2 Te 3 scraps, thereby improving the thermoelectric performance and obtaining a higher ZT value of 1.2.

Microstructure engineering is an effective strategy to reduce lattice thermal conductivity (κ l ) and enhance the thermoelectric figure of merit (zT). Through a new process based on melt-centrifugation to squeeze out excess eutectic liquid, microstructure modulation is realized to manipulate the formation of dislocations and clean grain boundaries, resulting in a porous network with a platelet structure. In this way, phonon transport is strongly disrupted by a combination of porosity, pore surfaces/junctions, grain boundaries, and lattice dislocations. These collectively result in a ≈60% reduction of κ l compared to zone melted ingot, while the charge carriers remain relatively mobile across the liquid-fused grains. This porous material displays a zT value of 1.2, which is higher than fully dense conventional zone melted ingots and hot pressed (Bi,Sb) 2 Te 3 alloys. A segmented leg of melt-centrifuged Bi 0.5 Sb 1.5 Te 3 and Bi 0.3 Sb 1.7 Te 3 could produce a high device ZT exceeding 1.0 over the whole temperature range of 323-523 K and an efficiency up to 9%. The present work demonstrates a method for synthesizing high-efficiency porous thermoelectric materials through an unconventional melt-centrifugation technique., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)