Bismuth Telluride/Half‐Heusler Segmented Thermoelectric Unicouple Modules Provide 12% Conversion Efficiency

Abstract

The rapid enhancement of the thermoelectric (TE) figure‐of‐merit (zT) in the past decade has opened opportunities for developing and transitioning solid state waste heat recovery systems. Here, a segmented TE device architecture is demonstrated in conjunction with heterogeneous material integration that results in high unicouple‐level conversion efficiency of 12% under a temperature difference of 584 K. This breakthrough is the result of success in fabricating bismuth telluride/half‐Heusler segmented TE unicouple modules using a “hot‐to‐cold” fabrication technique that provides significantly reduced electrical and thermal contact resistance. Extensive analytical and finite element modeling is conducted to provide an understanding of the nature of thermal transport and contributions arising from various thermal and physical parameters. Bismuth telluride/half‐Heusler based segmented thermoelectric generators (TEGs) can provide higher practical temperature difference with optimum average zT across the whole operating range. These results will have immediate impact on the design and development of TEGs and in the general design of devices based upon heterostructures that take advantage of gradients in the figure of merit.

Fabrication and Evaluation of Low-Cost CrSi2 Thermoelectric Legs

“…However, the efficiency of current commercial TE modules composed of state-of-the-art materials with ZT > 1 remains below ≈8% which strongly limits their use to niche applications [1,2]. With the aim to increase the applicability of this technology, many attempts to improve the overall performance of TE modules have been reported recently in the literature and consist of using newly developed materials with an improved ZT [3][4][5][6][7], the development of alternative architectures [8][9][10][11][12][13], or fabrication process [14]. However, two important challenges remain: (i) the use of less toxic and expensive elements than those comprising the majority of current high-performance materials (Pb, Te, Bi.…”

A Review on Fundamentals, Design and Optimization to High ZT of Thermoelectric Materials for Application to Thermoelectric Technology

“…172 There are modules available with excellent TE efficiency, which are deployed with high-performance thermoelectric materials such as half-Heusler materials, 113,[175][176][177] skutterudites, [178][179][180] and Bi 2 Te 3 . [181][182][183] For instance, Kang et al 113 186 recently achieved a high efficiency of 12% by fabricating a BiTe/HH unicouple module under a temperature gradient of 584 K. Zhang et al 187 have also fabricated the segmented modules consisting of Bi 2 Te 3 and CoSb 3 -based compounds, and achieved a high efficiency of 12% at a temperature gradient of 541 K. In very recent research, a unicouple module consisting of Mg 3.2 Bi 1.29 Sb 0.7 Te 0.01 as the n-type leg and Bi 0.2 Sb 1.8 Te 3 as the p-type leg was constructed, and had a reported efficiency of 9% for a temperature difference of 265 K. 188 Moreover, Bohra et al 189 designed a segmented thermoelement comprising of Bi 1.95 Pb 0.05 Te 3 and (AgSbTe2) 0.15 (GeTe) 0.85 , which exhibited an efficiency of 12% at a temperature difference of 494 K. Besides this, the thermoelectric efficiencies for SiGe-based alloys have reached ∼ 6.5%. 190,191 Interestingly, a high efficiency of ∼ 12% was obtained in a cascade Bi 2 Te 3 /nanostructured PbTe module.…”

The efficiency of short sintering time on thermoelectric properties of delafossite CuCr0:85Mg0:15O2 ceramics

“…Thermoelectric materials have recently emerged as a potential candidate for harvesting the waste heat from artificial sources: vehicles using the robust engines, thermal power plants, … or natural sources: geothermal or solar energy. Thermoelectric devices convert heat energy based on the dimensionless figure of merit ZT = σ .S 2 .T/(κ e + κ l ) 1 , where σ (S/cm) is electrical conductivity, S (µV/K) is Seebeck coefficient, κ e is electron thermal conductivity and κ l is lattice thermal conductivity. Therefore, a material that serves for thermoelectric device needs the ZT value is as high as possible.…”

“…Hence, the transport parameters (Seebeck coefficient, electrical, and thermal conductivity) need to be improved. However, these transport parameters commonly vanish to each other (e.g., the increase of electrical conductivity as elevating temperature gives rise to the decrease of Seebeck coefficient and the growth of thermal conductivity because of bipolar effect 1 ). Therefore, it is important to explore a material that could compromise those transport parameters.…”

“…Therefore, it is important to explore a material that could compromise those transport parameters. Recently, oxide materials emerge as a potential candidate for thermoelectric applications due to their advantages: (i) the stability of oxide compounds when it is exposed on ambient air at high temperature led to enhance the ZT value as following equation 1 ; (ii) the raw materials have low cost and environmental friendliness 2 . There are a number of thermoelectric oxide materials reported with high thermoelectric performance, such as SrTiO 3 , Ca 3 Co 4 O 9 , Na x CoO 2 , ZnO, In 2 O 3 , and BiCuSeO 3 .…”