What is it about?
This paper reports about a new four-step analysis method for thermoelectric (TE) materials. While the Seebeck coefficient is usually measured under small temperature gradient, we report here the measurement of TE materials under large temperature gradient. The examined materials were Ag- and Bi-doped Mg2Si, Si80Ge20, the ceramic composite NaTaO3-Fe2O3, the half-Heusler alloy (TiZr)NiSn, and the clathrates Ba8CuxSi48-x with x=8, 12.
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Why is it important?
The results show that the latter two metallic-like material groups have a low internal resistance. Hence, their output power is achieved at large electric currents with high carrier concentrations, while ceramic and silicides show the maximum output power at lower carrier concentration, which is considered to be a result of their large effective masses. The Arrhenius plot of the output energy yielded isosbestic-like points for ceramic-like materials, while the metal-like specimens show constant activation energies in the order of less than 0.1 eV. While all compared materials have reported ZT values around 0.4, the output energy was similar and measured as around 0.01 mW.
Perspectives
Advantages of the metallic TE materials are their high carrier concentration and easy processing, disadvantages are their sensitivity to impurities and oxidation. This paper is considered as a new standard for mneasuring thermoelectric materials.
Professor Wilfried Wunderlich
Tokai University Faculty of Engineering
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This page is a summary of: Energy Harvesting under Large Temperature Gradient – Comparison of Silicides, Half-Heusler Alloys and Ceramics, March 2018, De Gruyter,
DOI: 10.1515/energyo.0023.00031.
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