Dataset Information

Ultrahigh Power Factor in Thermoelectric System Nb_0.95M_0.05FeSb (M = Hf, Zr, and Ti).

ABSTRACT: Conversion efficiency and output power are crucial parameters for thermoelectric power generation that highly rely on figure of merit ZT and power factor (PF), respectively. Therefore, the synergistic optimization of electrical and thermal properties is imperative instead of optimizing just ZT by thermal conductivity reduction or just PF by electron transport enhancement. Here, it is demonstrated that Nb_0.95Hf_0.05FeSb has not only ultrahigh PF over ?100 µW cm^-1 K^-2 at room temperature but also the highest ZT in a material system Nb_0.95M_0.05FeSb (M = Hf, Zr, Ti). It is found that Hf dopant is capable to simultaneously supply carriers for mobility optimization and introduce atomic disorder for reducing lattice thermal conductivity. As a result, Nb_0.95Hf_0.05FeSb distinguishes itself from other outstanding NbFeSb-based materials in both the PF and ZT. Additionally, a large output power density of ?21.6 W cm^-2 is achieved based on a single-leg device under a temperature difference of ?560 K, showing the realistic prospect of the ultrahigh PF for power generation.

SUBMITTER: Ren W

PROVIDER: S-EPMC6051200 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Publications

Ultrahigh Power Factor in Thermoelectric System Nb0.95M0.05FeSb (M = Hf, Zr, and Ti).

Ren Wuyang W Zhu Hangtian H Zhu Qing Q Saparamadu Udara U He Ran R Liu Zihang Z Mao Jun J Wang Chao C Nielsch Kornelius K Wang Zhiming Z Ren Zhifeng Z

Advanced science (Weinheim, Baden-Wurttemberg, Germany) 20180502 7

Conversion efficiency and output power are crucial parameters for thermoelectric power generation that highly rely on figure of merit ZT and power factor (PF), respectively. Therefore, the synergistic optimization of electrical and thermal properties is imperative instead of optimizing just ZT by thermal conductivity reduction or just PF by electron transport enhancement. Here, it is demonstrated that Nb0.95Hf0.05FeSb has not only ultrahigh PF over ≈100 µW cm< ...[more]

PMID: 30027058

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Project description:Coating system(s) will be required for Nb-silicide based alloys. Alumina forming alloys that are chemically compatible with the Nb-silicide based alloy substrate could be components of such systems. The intermetallic alloys Nb1.45Si2.7Ti2.25Al3.25Hf0.35 (MG5) and Nb1.35Si2.3Ti2.3Al3.7Hf0.35 (MG6) were studied in the cast, heat treated and isothermally oxidised conditions at 800 and 1200 °C to find out if they are αAl₂O₃ scale formers. A (Al/Si)alloy versus Nb/(Ti + Hf)alloy map, which can be considered to be a map for Multi-Principle Element or Complex Concentrated Nb-Ti-Si-Al-Hf alloys, and a [Nb/(Ti + Hf)]Nb5Si3 versus [Nb/(Ti + Hf)]alloy map were constructed making use of the alloy design methodology NICE and data from a previously studied alloy, and were used to select the alloys MG5 and MG6 that were expected (i) not to pest, (ii) to form αAl₂O₃ scale at 1200 °C, (iii) to have no solid solution, (iv) to form only hexagonal Nb₅Si₃ and (v) to have microstructures consisting of hexagonal Nb₅Si₃, Ti₅Si₃, Ti₅Si₄, TiSi silicides, and tri-aluminides and Al rich TiAl. Both alloys met the requirements (i) to (v). The alumina scale was able to self-heal at 1200 °C. Liquation in the alloy MG6 at 1200 °C was linked with the formation of a eutectic like structure and the TiAl aluminide in the cast alloy. Key to the oxidation of the alloys was the formation (i) of "composite" silicide grains in which the Nb₅Si₃ core was surrounded by the Ti₅Si₄ and TiSi silicides, and (ii) of tri-aluminides with high Al/Si ratio, particularly at 1200 °C and very low Nb/Ti ratio forming in-between the "composite" silicide grains. Both alloys met the "standard definition" of high entropy alloys (HEAs). Compared with HEAs with bcc solid solution and intermetallics, the VEC values of both the alloys were outside the range of reported values. The parameters VEC,  and  of Nb-Ti-Si-Al-Hf coating alloys and non-pesting Nb-silicide based alloys were compared and trends were established. Selection of coating alloys with possible "layered" structures was discussed and alloy compositions were proposed.

Dataset Information

Ultrahigh Power Factor in Thermoelectric System Nb_0.95M_0.05FeSb (M = Hf, Zr, and Ti).

Publications

Ultrahigh Power Factor in Thermoelectric System Nb<sub>0.95</sub>M<sub>0.05</sub>FeSb (M = Hf, Zr, and Ti).

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