Realizing a 14% single-leg thermoelectric efficiency in GeTe alloys

Abstract

GeTe alloys have recently attracted wide attention as efficient thermoelectrics. In this work, a single-leg thermoelectric device with a conversion efficiency as high as 14% under a temperature gradient of 440 K was fabricated on the basis of GeTe-Cu2Te-PbSe alloys, which show a peak thermoelectric figure of merit (zT) > 2.5 and an average zT of 1.8 within working temperatures. The high performance of the material is electronically attributed to the carrier concentration optimization and thermally due to the strengthened phonon scattering, the effects of which all originate from the defects in the alloys. A design of Ag/SnTe/GeTe contact successfully enables both a prevention of chemical diffusion and an interfacial contact resistivity of 8 microhm·cm2 for the realization of highly efficient devices with a good service stability/durability. Not only the material’s high performance but also the device’s high efficiency demonstrated the extraordinariness of GeTe alloys for efficient thermoelectric waste-heat recovery.

A record thermoelectric efficiency in tellurium-free modules for low-grade waste heat recovery

“…1 ) are given in the Supplementary. A copper bar with known thermal conductivity was used as a heat-flow meter within a temperature difference of 0.6–2.3 K, which is determined by averaging 60 measurements with a relative standard deviation of <3% 36 (Supplementary Table 2 , Supplementary Fig. 2 ).…”

“…The Seebeck coefficient was determined by the slope of thermopower versus temperature difference within 0–5 K recorded by two K-type thermocouples attached to the edges of a radial direction of the sample. The thermal conductivity ( к ) is estimated by к = dC p D , where d is the density, C p is the heat capacity of the Dulong-Petit limit, D is the thermal diffusivity measured using a laser flash technique (Netzsch LFA467) 36 . Transport property measurements were performed within 300–600 K and the uncertainty of each was about 5%.…”

Fabrication and Evaluation of Low-Cost CrSi2 Thermoelectric Legs

“…where α = 100 µV K −1 , ρ = 10.0 µΩ m, and κ = 10.5 W m −1 K −1 are the Seebeck coefficient, the electrical resistivity, and thermal conductivity, respectively, of undoped CrSi 2 at 298 K taken from [15,41], A is the cross-section area of the leg, d the length of the leg, T h = 736 K the hot-side temperature; T c = 309 K the cold-side temperature, and ZT avg = 0.085 the figure of merit ZT of CrSi 2 at the average temperature T avg = 522 K. It should be noted that relations (5) to (8) were based on the constant properties model, i.e., no variation of the TE properties with the temperature, which was not rigorously the case for CrSi 2 [42]. However, in the present case, the low ∆T = 50 K made the variation of the properties negligible between the hot and cold sides and these relations were, thus, considered as acceptable models to predict V oc , R, and Q out .…”

“…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.…”

Optimizing thermocouple’s ZT through design innovation

“…2 .

Figure 2 Upper zT -envelopes constructed from the existing data for: SnSe 9 – 11 , Cu2Se 12 – 16 , GeTe 17 – 22 , PbTe 23 – 27 , PbS 28 – 31 , SnTe 32 – 39 , Bi Te 40 – 44 , Skutterudites 45 – 49 , BiCuSeO 50 – 52 , SiGe 53 – 56 , Half-Heuslers 57 – 61 . The lines are only for differentiating one group of materials from the other.

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