Qualification of Fe0.95Co0.05Si2 as a reference material for high temperature measurement of the thermoelectric power factor

Ziółkowski, Pawel; Edler, Frank; Stiewe, Christian; Haupt, Sebastian; Huang, Kai; Ryu, Byungki; Park, Su-Dong; Dasgupta, Titas; Sahu, Prashant; Taubmann, Rebekka; Müller, Eckhard

doi:10.1016/j.measurement.2022.112359

Cited by 8 publications

(7 citation statements)

References 32 publications

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“…For the measurement of the temperature dependent Seebeck coefficient and electrical conductivity, an in-house built setup was used . A custom-built Hall measurement setup was also used to measure the Hall coefficient as a function of temperature.…”

Section: Methodsmentioning

confidence: 99%

Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg₃(Sb_1–xBi_x)₂ Thermoelectric Materials

Suryawanshi,

Agrawal,

Kumari

et al. 2024

ACS Appl. Mater. Interfaces

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In recent years, bismuth-rich Mg 3 (Sb 1−x Bi x ) 2 (x = 0.5−0.8) compositions have generated significant interest due to their excellent thermoelectric (TE) performance near room temperature, making them potential applicants for recovery of low-grade waste heat. The superior performance in these materials is due to its complex electronic band structure (EBS) with presence of multiple near degenerate bands close to the conduction band edge. The position and curvature of these bands strongly depend on the alloy composition, doping amount as well as temperature. Thus, identifying optimal material compositions to get the best TE performance depends on an understanding of the temperature dynamics of EBS and forms the objective of this work. Mg 3 Sb 0.6 Bi 1.4 (x = 0.7) is chosen for this study due to its reported high near room temperature performance, and compositions with varying doping concentrations (Te used as dopant) have been synthesized. EBS parameters like effective mass and deformation potential of bands, interband separation and band gap values have been estimated using a recently developed refinement approach. Refinement results indicate that the interband separation between conduction bands to be a function of both temperature and doping concentration. Further, thermal conductivity (κ) was estimated for all of the compositions. Utilizing the EBS and κ information, predictive 3D maps indicating the variation in zT (TE figure of merit) with doping concentration and temperature have been generated. The 3D maps reveal an interesting surface topography with a broad peak zT region. This observation explains why these materials have high TE performance and are less sensitive to doping inhomogeneities. Our results provide detailed EBS information and fundamental insights on the TE properties of Mg 3 Sb 0.6 Bi 1.4 . Further, the proposed technique can be utilized to probe other Mg 3 (Sb 1−x Bi x ) 2 compositions and TE materials. KEYWORDS: thermoelectric materials, Mg 3 Sb 0.6 Bi 1.4 , electronic band structure modeling, charge transport measurements, thermoelectric figure of merit

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Section: Methodsmentioning

confidence: 99%

Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg₃(Sb_1–xBi_x)₂ Thermoelectric Materials

Suryawanshi,

Agrawal,

Kumari

et al. 2024

ACS Appl. Mater. Interfaces

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“…For the evaluation of the TE properties of Mg 2 (Si 0.3 Sn 0.7 ) 0.98 Bi 0.02 and Bi 2 (Te 2.7 Se 0.3 ) 0.98 (CuI) 0.02 , the Cu contacts were diced off and the disks obtained from the central portion were used. The combined measurements of electrical conductivity and Seebeck coefficient were carried out using a custom-made setup . The principle of electrical conductivity measurement was based on the van der Pauw method, while the slope method was used to obtain the Seebeck coefficient .…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The combined measurements of electrical conductivity and Seebeck coefficient were carried out using a custom-made setup. 36 The principle of electrical conductivity measurement was based on the van der Pauw method, while the slope method was used to obtain the Seebeck coefficient. 36 The thermal conductivity was obtained using a xenon-flash apparatus (LFA 467 HT, NETZSCH GmbH, Germany).…”

Section: Characterizationmentioning

confidence: 99%

“…36 The principle of electrical conductivity measurement was based on the van der Pauw method, while the slope method was used to obtain the Seebeck coefficient. 36 The thermal conductivity was obtained using a xenon-flash apparatus (LFA 467 HT, NETZSCH GmbH, Germany). All TE property measurements were carried out until 700 K for Mg 2 (Si 0.3 Sn 0.7 ) 0.98 Bi 0.02 and until 573 K for Bi 2 (Te 2.7 Se 0.3 ) 0.98 (CuI) 0.02 under an inert argon atmosphere.…”

Section: Characterizationmentioning

confidence: 99%

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A Constant Properties Model for the Performance Estimation in Segmented Thermoelectric Generator Elements and Its Experimental Validation Using an n-Type Mg₂Si_0.3Sn_0.7–Bi₂Te_2.7Se_0.3 Segmented Leg

Jayachandran

Dasgupta

Singh

2023

ACS Appl. Energy Mater.

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Segmenting multiple compatible thermoelectric (TE) materials can improve the conversion efficiency in thermoelectric generators (TEGs) compared to single-material TEGs. A model to accurately estimate the performance in segmented TEGs is essential for optimizing the geometric parameters. Constant properties models (CPMs) help in the quick estimation of the performance of TEGs working under large temperature differences using averaged material properties. This work discusses a CPM to predict the performance of single and segmented TEG elements using a combination of temperature-averaged and spatially-averaged TE properties. Spatial averaging requires the knowledge of the temperature profile across the TEG element length, which was obtained by solving the heat balance equation with a numerical integration approach as suggested by Ponnusamy et al. In this work, we develop the CPM for the segmented TEG elements (CPMS). The model predictions were validated experimentally from the performance evaluation of single Mg 2 (Si 0.3 Sn 0.7 ) 0.98 Bi 0.02 and segmented Mg 2 (Si 0.3 Sn 0.7 ) 0.98 Bi 0.02 − Bi 2 (Te 2.7 Se 0.3 ) 0.98 (CuI) 0.02 TEG elements. Single and segmented TEG elements with Cu contacts were prepared by a hot-pressing technique. Both Mg 2 (Si 0.3 Sn 0.7 ) 0.98 Bi 0.02 and Bi 2 (Te 2.7 Se 0.3 ) 0.98 (CuI) 0.02 TE materials show peak zT > 1 in their measurement range. The experimental results show a maximum efficiency (η max ) of ∼8.25% with 18% improvement for the segmented structure at ΔT ≈ 302 K. The improvement mainly originated from lower heat input (Q in ) even though the maximum power output (P max ) became lower by ∼30%. The performance prediction using the CPM matches well with <10% error for P max and η max for the single TEG element, and using the CPMS, the predictions were <10% error for P max and <25% error for η max for the segmented TEG element experimental results. This work demonstrates how CPMS can be used to predict device performance characteristics in segmented TEGs.

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“…Temperature dependent electrical conductivity (σ) and Seebeck coefficient ( S ) have been measured using an in-house built setup which can sequentially measure both these properties during a measurement cycle (300 K-723 K). The electrical conductivity is measured using the Van der-Pauw method while the measurement of S is based on the slope method .…”

Section: Methodsmentioning

confidence: 99%

Strained Lamellar Structures Leading to Improved Thermoelectric Performance in Mg₃Sb_1.5Bi_0.5

Kumari,

Pai,

Chavan

et al. 2023

ACS Appl. Mater. Interfaces

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Mg 3 Sb 2-x Bi x solid-solutions represent an important class of thermoelectric (TE) materials due to their high efficiency and variable operating temperature range. Of particular significance for midtemperature applications is the Mg 3 Sb 1.5 Bi 0.5 composition whose superior thermoelectric (TE) performance is attributed to the complex conduction band edge in conjunction with alloy dominated phonon scattering. In this work, we show that microstructure also plays a significant role in lowering the lattice thermal conductivity which in turn affects the overall TE performance (change in peak zT values between 1.1 and 1.4 have been observed). Temperature dependent TE properties of Mg 3+x Sb 1.5 Bi 0.5 compositions with varying nominal Mg content (x = 0.2, 0.3, 0.4) have been studied. A marked reduction of the lattice thermal conductivity (κ L ) is observed in compositions with low nominal Mg content (x = 0.2), which is due to the presence of lamellar structures within the grains. These lamellar regions are isostructural to the matrix with a low misfit angle and represent compositional fluctuations in the Bi to Sb ratio. Both the size (200 nm-500 nm) and the interfacial strain contribute to the enhanced phonon scattering. A quantitative estimate of κ L reduction due to these structures have been carried out using a mean free path (MFP) spectrum analysis which reveal a good match with experiments at room temperature. Further, the electrical properties are not influenced by these lamellar structures as observed from the similar power-factor (S 2 σ) and weighted mobilities in all of the compositions. This is due to their similar orientation to the adjacent matrix region. Thus, the zT parameter in the various compositions with similar carrier concentration can be significantly altered (∼25%) by adjusting the nominal Mg content. The results demonstrate that preferential phonon scattering by microstructure modification can be a new route for property improvement in Mg 3+x Sb 2−y Bi y solid-solutions.

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Qualification of Fe0.95Co0.05Si2 as a reference material for high temperature measurement of the thermoelectric power factor

Cited by 8 publications

References 32 publications

Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg₃(Sb_1–xBi_x)₂ Thermoelectric Materials

Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg₃(Sb_1–xBi_x)₂ Thermoelectric Materials

A Constant Properties Model for the Performance Estimation in Segmented Thermoelectric Generator Elements and Its Experimental Validation Using an n-Type Mg₂Si_0.3Sn_0.7–Bi₂Te_2.7Se_0.3 Segmented Leg

Strained Lamellar Structures Leading to Improved Thermoelectric Performance in Mg₃Sb_1.5Bi_0.5

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Qualification of Fe0.95Co0.05Si2 as a reference material for high temperature measurement of the thermoelectric power factor

Cited by 8 publications

References 32 publications

Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg3(Sb1–xBix)2 Thermoelectric Materials

Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg3(Sb1–xBix)2 Thermoelectric Materials

A Constant Properties Model for the Performance Estimation in Segmented Thermoelectric Generator Elements and Its Experimental Validation Using an n-Type Mg2Si0.3Sn0.7–Bi2Te2.7Se0.3 Segmented Leg

Strained Lamellar Structures Leading to Improved Thermoelectric Performance in Mg3Sb1.5Bi0.5

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Product

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Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg₃(Sb_1–xBi_x)₂ Thermoelectric Materials

Developing a Multiband Electronic Band Structure Model and Predictive Maps for Bismuth-Rich Mg₃(Sb_1–xBi_x)₂ Thermoelectric Materials

A Constant Properties Model for the Performance Estimation in Segmented Thermoelectric Generator Elements and Its Experimental Validation Using an n-Type Mg₂Si_0.3Sn_0.7–Bi₂Te_2.7Se_0.3 Segmented Leg

Strained Lamellar Structures Leading to Improved Thermoelectric Performance in Mg₃Sb_1.5Bi_0.5