Characterization of the thermo-mechanical properties of p-type (MnSi1.77) and n-type (Mg2Si0.6Sn0.4) thermoelectric materials

Mejri, Mahdi; Thimont, Yohann; Malard, B.; Estournès, Claude

doi:10.1016/j.scriptamat.2019.06.037

Cited by 21 publications

(18 citation statements)

References 31 publications

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“…Fig. 1a presents a TEG manufactured by the industrial Partner HBOB with two legs of high manganese silicide (HMS) and two legs of Mg 2 Si 0.55 Sn 0.45 [8]. The generator was obtained by soldering the thermoelectric legs with metallized ceramics plates (AlN-DBC) using a silver solder.…”

Section: Methodsmentioning

confidence: 99%

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Thermal stability of Mg2Si0.55Sn0.45 for thermoelectric applications

Mejri

Malard

Thimont

et al. 2020

Journal of Alloys and Compounds

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Understanding the thermal stability of the Mg 2 (Si,Sn) system is essential to define their safe temperatures of service. Despite its good thermoelectric performance, Mg 2 (Si,Sn) is subject to a phase separation during thermal cycling due to the miscibility gap, which leads to a degradation of its thermoelectric properties and affects its performance during device operation. Isothermal annealing at 500 C and 750 C were performed with different annealing time to investigate thermal stability of Mg 2 (Si,Sn). During the heat treatment, two phases were formed associated with porosity in the matrix. In addition, thickness of specimen was tracked and a significant expansion was detected. This phenomenon is attributed to the Kirkendall effect. The composition and the structure of the two forming phases were investigated by electron probe microanalysis and X-ray diffraction. Finally, the optimized thermal treatment allowed to stabilize the Mg 2 (Si,Sn) without porosity and the presence of two thermodynamically stabilized phase (Mg 2 Si 0.41 Sn 0.59 and Mg 2 Si 0.58 Sn 0.42) leading to a better reliability of the silicide thermoelectric modules.

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Section: Methodsmentioning

confidence: 99%

“…The difference between the diffusion coefficients of Sn and Si generate a lacuna flux, which provide voids located in the Sn-rich (matrix). This effect is known as the Kirkendall effect [29] and lead to the presence of porosity which can reduce the mechanical properties of the material [8].…”

Section: Structural and Microstructural Properties Of Mg 2 Si 055 Snmentioning

confidence: 99%

Thermal stability of Mg2Si0.55Sn0.45 for thermoelectric applications

Mejri

Malard

Thimont

et al. 2020

Journal of Alloys and Compounds

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“…For the model, the intrinsic, temperature dependent material properties from experi mental measurements were used. Experimental details for HMS (MnSi y where 1.73 < y < 1.77), including its emissivity, are reported elsewhere, 40 and the temperature dependent functional forms of the Seebeck coefficient, electrical conductivity, and thermal conductivity valid for the temperature range 30°C 530°C are as follows:…”

Section: Modeling Approachmentioning

confidence: 99%

“…For HMS, the emissivity was measured experimentally at 0.6. 40 The emissivity of bismuth telluride was taken as 0.66 from Ref. 41, but this material property is not widely characterized for thermoelectric materials, even a common one such as bismuth telluride.…”

Section: Modeling Approachmentioning

confidence: 99%

“…43 This design reduces the mechanical stress induced in the thermoelectric material due to the differences in thermomechanical properties (e.g , coeffi cient of thermal expansion) of the substrate, metal shunts, and thermoelectric materials. 40 The reduction of mechanical stress in thermoelectric modules improves reliability, particularly in applica tions with thermal cycling. The reduced substrate research and development advancement is incorporated in these module simula tions; there is no top (cold side) substrate.…”

Section: Vertical Classificationmentioning

confidence: 99%

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The impact of thermoelectric leg geometries on thermal resistance and power output

Thimont

LeBlanc

2019

Journal of Applied Physics

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Thermoelectric devi ces enable direct, solid state conversion of heat to electricity and vice versa. Rather than designing the shape of thermo electric units or l eg s to maximize this energy conversion, the cuboid shape of these l eg s has instead remained unchanged in large part because of limitations in the standard manufacturing process. However, the advent of additive manufacturing (a technique in which freeform geometries are built up l aye r by l aye r) offers the potential to create unique thermoelectric leg geometries desi gn ed to optimize device performance. This work explores this new realm of nove! leg geometry by simulating the thermal and electrical performance of various leg geometries such as prismatic, hollow, and layered structures. The simulations are performed for two materials, a standard bismuth telluride material found in current commercial modules and a higher manganese silicide material proposed for low cost energy conversion in high temperature applications. The results indude the temperature gradient and electrical potential developed across individual thermoelectric legs as well as thermoelectric modules with 16 legs. Even simple hollow and layered l eg geometries result in larger temperature gradients and higher output powers than the traditional cuboid structure. The clear dependence of thermal resistance and power output on leg geometry provides compelling motivation to explore additive manufacturing of thermoelectric devices.

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Efficiency Measurement and Modeling of a High‐Performance Mg₂(Si,Sn)‐Based Thermoelectric Generator

et al. 2022

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Mg2(Si,Sn) is an attractive material class due to its excellent thermoelectric (TE) properties, its eco‐friendly constituents, its low mass density, and its low price. A lot of research has been done on optimizing its TE properties; however, works on its use in thermoelectric generators (TEG) are scarce. Herein, the first conversion efficiency measurement of a functional, fully Mg2(Si,Sn)‐based TEG, approaching a maximum value of 4% for an applied ΔT = 375 °C, is shown. A maximum power density of 0.9 W cm−2 (related to the cross‐sectional area of the TE legs) at ΔT=375 °C is also reported, which is among the highest performance of silicide‐based modules reported in literature. Efficiency measurements can be tricky due to the uncertainty of heat flow measurement and parasitic heat losses; therefore, assessing the measurement reliability by confronting it to theoretical calculations is necessary. TEG device simulation in a constant property model is used to compare measured data to expected values and a good match is found (<1% deviation for current at maximum power, <4% difference for maximum power output, deviation within measurement uncertainty range for heat flows and efficiency). The significant discrepancy between measurement and calculations of the inner electrical resistance reveals room for improvement. Cracks form due to thermally induced mechanical stress, which dramatically increase the inner electrical resistance. It is shown that by avoiding those cracks, the maximum power output and conversion efficiency of the TEG could be improved by 30%.

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Characterization of the thermo-mechanical properties of p-type (MnSi1.77) and n-type (Mg2Si0.6Sn0.4) thermoelectric materials

Abstract: Characterization of the thermo-mechanical properties of p-type (MnSi1.77) and n-type (Mg2Si0.6Sn0.4) thermoelectric materials. (2019) Scripta Materialia, 172. 28-32.

Cited by 21 publications

References 31 publications

Thermal stability of Mg2Si0.55Sn0.45 for thermoelectric applications

Thermal stability of Mg2Si0.55Sn0.45 for thermoelectric applications

The impact of thermoelectric leg geometries on thermal resistance and power output

Efficiency Measurement and Modeling of a High‐Performance Mg₂(Si,Sn)‐Based Thermoelectric Generator

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Characterization of the thermo-mechanical properties of p-type (MnSi1.77) and n-type (Mg2Si0.6Sn0.4) thermoelectric materials

Abstract: Characterization of the thermo-mechanical properties of p-type (MnSi1.77) and n-type (Mg2Si0.6Sn0.4) thermoelectric materials. (2019) Scripta Materialia, 172. 28-32.

Cited by 21 publications

References 31 publications

Thermal stability of Mg2Si0.55Sn0.45 for thermoelectric applications

Thermal stability of Mg2Si0.55Sn0.45 for thermoelectric applications

The impact of thermoelectric leg geometries on thermal resistance and power output

Efficiency Measurement and Modeling of a High‐Performance Mg2(Si,Sn)‐Based Thermoelectric Generator

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Product

Resources

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Efficiency Measurement and Modeling of a High‐Performance Mg₂(Si,Sn)‐Based Thermoelectric Generator