The widespread application of thermoelectric (TE) technology demands high‐performance materials, which has stimulated unceasing efforts devoted to the performance enhancement of Bi2Te3‐based ...commercialized thermoelectric materials. This study highlights the importance of the synthesis process for high‐performance achievement and demonstrates that the enhancement of the thermoelectric performance of (Bi,Sb)2Te3 can be achieved by applying cyclic spark plasma sintering to BixSb2–xTe3‐Te above its eutectic temperature. This facile process results in a unique microstructure characterized by the growth of grains and plentiful nanostructures. The enlarged grains lead to high charge carrier mobility that boosts the power factor. The abundant dislocations originating from the plastic deformation during cyclic liquid phase sintering and the pinning effect by the Sb‐rich nano‐precipitates result in low lattice thermal conductivity. Therefore, a high ZT value of over 1.46 is achieved, which is 50% higher than conventionally spark‐plasma‐sintered (Bi,Sb)2Te3. The proposed cyclic spark plasma liquid phase sintering process for TE performance enhancement is validated by the representative (Bi,Sb)2Te3 thermoelectric alloy and is applicable for other telluride‐based materials.
The thermoelectric power factor and figure of merit of the BiSbTe alloy are significantly improved by cyclic liquid‐phase aided spark plasma sintering process. The present proposed fabrication process modulates the microstructure in a wide range of scale from nano‐sized dislocations to micrometer grain size, leading to a synergistic control of charge carriers and phonon transport.
Microstructure engineering is an effective strategy to reduce lattice thermal conductivity (κl) 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 κl 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)2Te3 alloys. A segmented leg of melt‐centrifuged Bi0.5Sb1.5Te3 and Bi0.3Sb1.7Te3 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.
The melt‐centrifugation technique is demonstrated to be able to decrease the thermal conductivity while preserving the good electrical properties. By introducing a unique porous structure with microscale dislocation, ≈60% reduction in lattice thermal conductivity compared to conventional zone melted ingots is achieved. Such a method paves a new way for top‐down introduction of large porosity and dense dislocations in bulk materials.
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 BiI3 sublimation technique, pore networks can be introduced into tetrahedrite Cu12Sb4S13‐based materials, accompanied by changes in their hierarchical structures. The addition of a small quantity of BiI3 (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.
A porous network structure with excellent electrical properties can enhance the thermoelectric performance of solid materials. This work demonstrates that a porous structure can be introduced into tetrahedrite‐based synthetic minerals by a unique BiI3 sublimation technique. The multiscale architectures simultaneously disrupt phonon transport and trigger energy‐dependent scattering of holes, leading to a superior zT value of 1.15 at 723 K.
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.
GeTe/(Bi,Sb)2Te3 segmented one‐leg thermoelectric modules are successfully designed and fabricated. Its maximum efficiency reaches 9.5 % under the adiabatic boundary condition of cold side heat flow via Mini‐PEM, indicating a good application prospect.
Abstract
GeTe is a promising mid-temperature thermoelectric compound but inevitably contains excessive Ge vacancies hindering its performance maximization. This work reveals that significant ...enhancement in the dimensionless figure of merit (
ZT
) could be realized by defect structure engineering from point defects to line and plane defects of Ge vacancies. The evolved defects including dislocations and nanodomains enhance phonon scattering to reduce lattice thermal conductivity in GeTe. The accumulation of cationic vacancies toward the formation of dislocations and planar defects weakens the scattering against electronic carriers, securing the carrier mobility and power factor. This synergistic effect on electronic and thermal transport properties remarkably increases the quality factor. As a result, a maximum
ZT
> 2.3 at 648 K and a record-high average
ZT
(300-798 K) were obtained for Bi
0.07
Ge
0.90
Te in lead-free GeTe-based compounds. This work demonstrates an important strategy for maximizing the thermoelectric performance of GeTe-based materials by engineering the defect structures, which could also be applied to other thermoelectric materials.
Mg3(Sb,Bi)2 is a potential nearly‐room temperature thermoelectric compound composed of earth‐abundant elements. However, complex defect tuning and exceptional microstructural control are required. ...Prior studies have confirmed the detrimental effect of Mg vacancies (VMg) in Mg3(Sb,Bi)2. This study proposes an approach to mitigating the negative scattering effect of VMg by Bi deficiency, synergistically modulating the electrical and thermal transport properties to enhance the thermoelectric performance. Positron annihilation spectrometry and Cs‐corrected scanning transmission electron microscopy analyses indicated that the VMg tends to coalesce due to the introduced Bi vacancies (VBi). The defects created by Bi deficiency effectively weaken the scattering of electrons from the intrinsic VMg and enhance phonon scattering. A peak zT of 1.82 at 773 K and high conversion efficiency of 11.3% at ∆T = 473 K are achieved in the optimized composition of Mg3(Sb,Bi)2 by tuning the defect combination. This work demonstrates a feasible and effective approach to improving the performance of Mg3(Sb,Bi)2 as an emerging thermoelectric material.
The formation and tuning of complex defects can effectively enhance the thermoelectric performance of Mg3(Sb,Bi)2. This work proposes an approach to mitigate the negative scattering effect of Mg vacancies by Bi deficiency. The heterovalent vacancies provide a strong phonon scattering, leading to a significant reduction of the lattice thermal conductivity and a superior zT.
Thermoelectric materials can directly convert heat to electricity and vice versa. ZT ( =S2σT/κ ) is usually used for evaluating the performance of thermoelectric materials. Improving ZT is a ...challenging task because of the strong interdependence among the Seebeck coefficient (S), electrical conductivity (σ) and thermal conductivity (κ). This review provides a summary of some promising thermoelectric materials in different developing stages with emphasis on the corresponding strategies for thermoelectric performance enhancement. In addition, the number of recent publications on some representative thermoelectric materials is summarized, addressing the current research interests in this field. Thermoelectricity still need intensified scientific efforts to meet the practical demand.
•Summarize most promising bulk thermoelectric materials.•Enumerate traditional thermoelectric materials and the corresponding performance enhancing strategies and developing status.•Some emerging and burgeoning materials with outstanding thermoelectric performance are reviewed.
Abstract
Mg
3
(Sb,Bi)
2
is a promising thermoelectric material suited for electronic cooling, but there is still room to optimize its low-temperature performance. This work realizes >200% enhancement ...in room-temperature
zT
by incorporating metallic inclusions (Nb or Ta) into the Mg
3
(Sb,Bi)
2
-based matrix. The electrical conductivity is boosted in the range of 300–450 K, whereas the corresponding Seebeck coefficients remain unchanged, leading to an exceptionally high room-temperature power factor >30 μW cm
−1
K
−2
; such an unusual effect originates mainly from the modified interfacial barriers. The reduced interfacial barriers are conducive to carrier transport at low and high temperatures. Furthermore, benefiting from the reduced lattice thermal conductivity, a record-high average
zT
> 1.5 and a maximum
zT
of 2.04 at 798 K are achieved, resulting in a high thermoelectric conversion efficiency of 15%. This work demonstrates an efficient nanocomposite strategy to enhance the wide-temperature-range thermoelectric performance of n-type Mg
3
(Sb,Bi)
2
, broadening their potential for practical applications.
An electrochemical sensor based on the composites of Pt nanoparticles modified carbon dots and ionic liquid-functionalized graphene oxide was fabricated for detection of H2O2 with high sensitivity ...and adequate selectivity.
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•Pt nanoparticles-carbon quantum dots (PtNPs-CDs)/IL-graphene oxide (IL-GO)/GCE electrode was used to detect H2O2.•PtNPs-CDs/IL-GO was used as an electrochemical sensing nanocomposite.•Synergistic amplifying effects resulted from combining PtNPs-CDs and IL-GO.•The sensor showed high sensitivity and selectivity, low detection limit and wide linear range to H2O2 using amperometry.•The sensor was used for successful H2O2 determination in real serum samples.
There is current interest in developing carbon nanomaterials, which are a novel kind of nanomaterial, for uses in electrochemical sensing and biosensors. We constructed a novel sensor based on a Pt nanoparticles-carbon quantum dots/ionic liquid functionalized graphene oxide (PtNPs-CDs/IL-GO) nanocomposite for detecting H2O2. We characterized the morphology and electrochemical performance of the modified electrode using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and cyclic voltammetry, respectively. The unique chemical structure of PtNPs-CDs/IL-GO greatly accelerated the catalysis of H2O2 and provided plenty of active sites for electrochemical redox reactions. Electrochemical experiments demonstrated that the PtNPs-CDs/IL-GO sensor had high selectivity, a wide linear range from 1 to 900μM, and a low detection limit of 0.1μM with respect to the reduction of H2O2. These characteristics indicate good electrical conductivity and high electrocatalytic activity. This simple and effective method has potential applications in chemical sensors and electrochemical catalysis.
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