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Electrical Contacts Characterization of Tetrahedrite-Based Thermoelectric Generators

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2022-06-08
JournalMATERIAIS 2022
AuthorsRodrigo Coelho, Yassine De Abreu, Francisco Carvalho, Elsa B. Lopes, A.P. Gonçalves
InstitutionsUniversity of Lisbon, Instituto Politécnico de Lisboa
Citations1
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research focuses on optimizing electrical contacts for sustainable, low-cost tetrahedrite-based Thermoelectric Generators (TEGs), addressing a critical barrier to commercial viability.

  • Core Value Proposition: Development of efficient, low-resistance electrical contacts for copper antimony sulfosalts (Cu11Mn1Sb4S13), a material class offering low toxicity and low cost (~USD 7).
  • Performance Baseline: The tetrahedrite material exhibits promising thermoelectric properties, achieving an average Figure of Merit (zT) ≥ 0.4 within the operational range of 350 K to 650 K.
  • Engineering Challenge: The primary focus is mitigating high electrical and thermal contact resistance between the tetrahedrite legs and copper electrodes, which severely degrades TEG performance.
  • Fabrication Methods Tested: Various jointing techniques were evaluated, including cold-pressing (CP), hot-pressing (HP), and the use of conductive jointing materials (Ni paint, Ag paint, and Zn-Al 5 wt% solder).
  • Characterization and Modeling: Contact resistance was quantified using a custom three-point pulsed current method. These measured values were then integrated into COMSOL Multiphysics simulations to predict final device Current-Voltage (IV) and Current-Power (IP) performance.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Thermoelectric MaterialCu11Mn1Sb4S13N/ASpecific tetrahedrite composition studied.
Material Cost (Estimate)~7USDEstimated low cost, supporting commercial competitiveness.
Figure of Merit (zT)≥ 0.4N/AAverage performance achieved by tetrahedrites.
Operational Temperature Range350 to 650KTemperature window for measured zT performance.
Leg Dimensions (Approx.)7 x 7mmSize of tetrahedrite cubes cut for contact testing.
Electrode MaterialCopperN/AMaterial used for electrical contacts.
Solder Composition TestedZn-Al 5wt%Solder used as a jointing material.
Resistance MeasurementThree-point pulsedCurrent MethodCustom setup used for contact resistance characterization.
Simulation ToolCOMSOLMultiphysicsUsed for predicting device IV and IP performance.

Key Methodologies

Section titled “Key Methodologies”

The study involved a structured approach covering material synthesis, shaping, diverse contact fabrication, and performance modeling.

  1. Material Synthesis and Sintering:
    • Tetrahedrite (Cu11Mn1Sb4S13) was synthesized using a solid-state reaction method.
    • The material was sintered and consolidated via hot-pressing to form dense TEG legs.
  2. Leg Preparation:
    • Sintered materials were shaped into small cubes (approximately 7 x 7 mm) using a Diamond saw.
  3. Contact Fabrication Techniques (Jointing):
    • Mechanical Pressing: Contacts were formed using both cold-pressing (CP) and hot-pressing (HP) methods.
    • Manual Preparation: A control group of legs was prepared manually for baseline comparison.
    • Solder/Paint Application: Three distinct jointing materials were tested between the tetrahedrite legs and copper plates:
      • Ni water-based paint.
      • Ag water-based paint.
      • Zn-Al 5 wt% solder.
    • Solderless HP: The feasibility of direct contact fabrication without any intermediate paints or solders was explored using hot-pressing equipment.
  4. Electrical Characterization:
    • Contact resistance between the tetrahedrites and copper contacts was measured using a custom-made setup based on the three-point pulsed current method.
  5. Performance Modeling:
    • Measured contact resistance values were incorporated into finite element simulations using COMSOL Multiphysics.
    • The simulations generated predictive current-voltage (IV) and current-power (IP) plots to evaluate how contact quality affects overall TEG performance.

Commercial Applications

Section titled “Commercial Applications”

The development of robust, low-resistance contacts for tetrahedrite materials directly supports the commercialization of cost-effective and sustainable thermoelectric devices.

  • Industrial Waste Heat Recovery: Deployment of TEG modules in manufacturing facilities to harvest low-to-mid grade waste heat (350 K to 650 K) from exhaust stacks, cooling systems, or process equipment, converting it into usable electricity.
  • Automotive and Transportation: Integration into vehicle exhaust systems to recover thermal energy, potentially powering auxiliary systems or improving overall fuel efficiency.
  • Sustainable and Green Energy Solutions: Utilizing non-toxic, earth-abundant materials (copper antimony sulfosalts) to create environmentally friendly power sources, aligning with global efforts to reduce reliance on toxic materials like tellurides.
  • Low-Cost Sensor Power: Providing reliable, maintenance-free power for remote sensors, IoT devices, and monitoring equipment by leveraging small ambient temperature gradients.
  • Mass Production of TEG Modules: The focus on optimizing scalable jointing techniques (e.g., hot-pressing, specific solders) facilitates the high-volume, cost-competitive manufacturing of TEG modules for various markets.
View Original Abstract

first_page settings Order Article Reprints Font Type: Arial Georgia Verdana Font Size: Aa Aa Aa Line Spacing:    Column Width:    Background: Open AccessAbstract Electrical Contacts Characterization of Tetrahedrite-Based Thermoelectric Generators † by Rodrigo Coelho 1,*, Yassine De Abreu 2, Francisco Carvalho 3, Elsa B. Lopes 1 and AntĂłnio P. Gonçalves 1 1 C2TN, DECN, Instituto Superior TĂ©cnico, Campus TecnolĂłgico e Nuclear, Universidade de Lisboa, 2695-066 Loures, Portugal 2 CESI, Campus D’enseignement SupĂ©rieur et de Formation Professionnelle, 15C Av. Albert Einstein, Villeurbanne, 69100 Lyon, France 3 DEEC, Instituto Superior TĂ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal * Author to whom correspondence should be addressed. † Presented at the Materiais 2022, Marinha Grande, Portugal, 10-13 April 2022. Mater. Proc. 2022, 8(1), 87; https://doi.org/10.3390/materproc2022008087 Published: 8 June 2022 (This article belongs to the Proceedings of MATERIAIS 2022) Download Download PDF Download PDF with Cover Download XML Download Epub Versions Notes Thermoelectric generators (TEGs) are devices capable of harvesting waste heat and directly converting it into electricity through the Seebeck effect. They have no moving parts and emit neither toxic nor greenhouse gasses. These devices have high modularity and low maintenance needs, making them very promising to fight against global warming. At the same time, with the rapid growth in energetic needs and the efforts from industries to become greener, the market for TEGs is boosting the search for more efficient and cheaper materials. One such new material, seen as having great potential for thermoelectric applications, is copper antimony sulfosalts. These materials are very cheap (~USD 7 [1]), can be found in nature, have good thermoelectric properties (average zT ≄ 0.4 between 350 K and 650 K [2]), and present low toxicities. However, tetrahedrite-based TEGs are still under development, with the fabrication of good electrical contacts between tetrahedrites and the copper electrodes (that form the device) being one of the biggest challenges to produce efficient and commercially competitive generators. Since high electrical and thermal resistivities can ruin the performance of TEGs, such problems can be also found in commercial devices. However, there are just a few public studies focused on measuring and characterizing the electrical contacts, with most of the jointing fabrication techniques being patented or classified [3].In the present work, diverse contact fabrication techniques are explored to evaluate the most suitable methods to connect Cu11Mn1Sb4S13 tetrahedrites to copper electrodes. The tetrahedrite legs were synthetized by a solid-state reaction and sintered by hot-pressing. Then, the materials were shaped into small cubes (~7 × 7 mm) using a Diamond saw and connected to copper plates (~7 × 7 mm) using different techniques. Contact fixation methods such as cold-pressing (CP) and hot-pressing (CP) were used, with some legs also being prepared manually. Together with the different preparation methods, several paints and resins were used for jointing. In summary, Ni and Ag water-based paints and a Zn-Al 5 wt% solder were tested. The possibility of contact fabrication without the use of any paints or solders was also explored by using our hot-pressing equipment.The contact resistance between the tetrahedrites and the copper contacts was measured in a custom-made set-up based on the three-point pulsed current method. To achieve a better understanding on how the contact quality affects the final performance of a tetrahedrite based TEG, several computer simulations were made using the COMSOL Multiphysics software. The previously measured contact resistance values were considered on the simulations, and the respective current-voltage (IV) and current-power (IP) plots for a thermocouple were obtained. The main results of this study on how different fabrication methods and jointing materials affect the electrical contact resistance and the performance of a tetrahedrite based TEG will be presented. Author ContributionsConceptualization, A.P.G. and R.C.; methodology, R.C.; software, E.B.L.; validation, R.C., E.B.L. and A.P.G.; formal analysis, R.C., E.B.L. and A.P.G.; investigation, R.C., Y.D.A. and F.C.; resources, E.B.L. and A.P.G.; data curation, R.C., Y.D.A. and F.C.; writing—original draft preparation, R.C., E.B.L. and A.P.G.; writing—review and editing, R.C., E.B.L. and A.P.G.; visualization, R.C., E.B.L. and A.P.G.; supervision, E.B.L. and A.P.G.; project administration, E.B.L. and A.P.G.; funding acquisition, R.C., E.B.L. and A.P.G. All authors have read and agreed to the published version of the manuscript.FundingThis work was supported by the Portuguese Foundation for Science and Technology (FCT), Portugal, through the contracts UID/Multi/04349/2020 and UI/BD/150713/2020.Institutional Review Board StatementNot Applicable.Informed Consent StatementNot Applicable.Data Availability StatementNot Applicable. Conflicts of InterestThe authors declare no conflict of interest.ReferencesGonçalves, A.P.; Lopes, E.B.; Monnier, J.; Alleno, E.; Godart, C.; Montemor, M.; Vaney, J. Tetrahedrites for low cost and sustainable thermoelectrics. Solid State Phenom. 2017, 257, 135-138. [Google Scholar] [CrossRef]Coelho, R.; Symeou, E.; Kyratsi, T.; Gonçalves, A.P. Tetrahedrite sintering conditions: The Cu11Mn1Sb4S13 case. J. Electr. Mater. 2020, 49, 5077-5083. [Google Scholar] [CrossRef]Ren, Z.; Lan, Y.; Zhang, Q. (Eds.) Advanced Thermoelectrics, Materials, Devices, Contacts and Systems; Taylor & Francis Group LLC.: New York, NY, USA, 2017. [Google Scholar] [CrossRef]Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Share and Cite MDPI and ACS Style Coelho, R.; De Abreu, Y.; Carvalho, F.; Lopes, E.B.; Gonçalves, A.P. Electrical Contacts Characterization of Tetrahedrite-Based Thermoelectric Generators. Mater. Proc. 2022, 8, 87. https://doi.org/10.3390/materproc2022008087 AMA Style Coelho R, De Abreu Y, Carvalho F, Lopes EB, Gonçalves AP. Electrical Contacts Characterization of Tetrahedrite-Based Thermoelectric Generators. Materials Proceedings. 2022; 8(1):87. https://doi.org/10.3390/materproc2022008087 Chicago/Turabian Style Coelho, Rodrigo, Yassine De Abreu, Francisco Carvalho, Elsa B. Lopes, and AntĂłnio P. Gonçalves. 2022. “Electrical Contacts Characterization of Tetrahedrite-Based Thermoelectric Generators” Materials Proceedings 8, no. 1: 87. https://doi.org/10.3390/materproc2022008087 Find Other Styles Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here. Article Metrics No No Article Access Statistics Multiple requests from the same IP address are counted as one view.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2017 - Tetrahedrites for low cost and sustainable thermoelectrics
  2. 2020 - Tetrahedrite sintering conditions: The Cu11Mn1Sb4S13 case [Crossref]

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