Scalable synthesis of n-type Mg3Sb2-xBix for thermoelectric applications

https://doi.org/10.1016/j.mtphys.2020.100336Get rights and content

Highlights

  • Scalable synthesis of n-type Mg3Sb2-xBix-based thermoelectrics.

  • Capable of satisfying cheap mass production of Mg3Sb2-xBix-based thermoelectrics.

  • Good thermoelectric performance, uniformity and high thermoelectric property of large-scale samples.

  • A peak efficiency of ∼12.9% was achieved in a Mg3.1Sb1.5Bi0.49Te0.01 single leg at the temperature difference of ∼480 K.

Abstract

The highly efficient n-type Mg3Sb2-xBix thermoelectric materials hold great promise for application in power generation as well as refrigeration. Currently, n-type Mg3Sb2-xBix compounds with high zTs can be easily reproduced on a laboratory scale with ∼10 g per batch. However, scaling up the synthesis of Mg3Sb2-xBix with uniform high thermoelectric performance, which is critical for promoting this compound for practical applications, has yet to be achieved. Here we report a scalable preparation method based on Simoloyer ball-milling, which allows us to obtain over 1 kg Mg3.1Sb1.5Bi0.49Te0.01 powder in a single batch. Subsequently, samples with different diameters (ranging from a half inch to two inches) were successfully prepared and their thermoelectric performance was found to be comparable. In addition, a two-inch sample was sectioned into several parts, and the thermoelectric properties of the separate parts are also similar, indicating the high uniformity of the prepared large-scale sample. Importantly, the single-leg Mg3.1Sb1.5Bi0.49Te0.01 attains a high energy conversion efficiency of ∼12.9% under a temperature difference of ∼480 K at the hot-side temperature of 773 K. This study represents a step toward the practical application of Mg3Sb2-xBix for thermoelectric power generation.

Section snippets

Credit author statement

Congcong Xu: Investigation–performing the experiments and data collection, Formal analysis, Writing–original draft. Zhongxin Liang: Investigation–performing the experiments and data collection, Formal analysis, Writing–original draft. Hongjing Shang: Formal analysis. Dezhi Wang: Investigation–performing the experiments and data collection. Hui Wang: Investigation–performing the experiments and data collection. Fazhu Ding: Data curation, Writing–review & editing. Jun Mao: Conceptualization,

Synthesis

Magnesium turnings (Mg, 99.98%; Alfa Aesar), bismuth pieces (Bi, 99.99%; Alfa Aesar), antimony shots (Sb, 99.8%; Alfa Aesar), and tellurium pieces (Te, 99.999%; Alfa Aesar) were weighed according to the composition of Mg3.1Sb1.5Bi0.49Te0.01 and with a total mass of 1200 g. Although the stoichiometric ratio of elemental Mg in the compound is generally 3.2, it was reduced to 3.1 in order to alleviate the cold-welding issue during the ball-milling process [8,33,40,41]. The Simoloyer ball-miller

Microstructure and composition of the prepared bulk samples

Experimentally, about 1.12 kg of Mg3.1Sb1.5Bi0.49Te0.01 fine powder was successfully obtained in a single batch of 1.2 kg starting raw materials (∼93% yield), as shown in Fig. S1 (Supporting Information). In principle, the Simoloyer ball-miller can process up to 3 kg of raw elements in total, so scaling up the synthesis even further is possible. The as-prepared powder was then hot-pressed into bulk samples with different diameters, i.e., 1/2 inch (∼12.70 mm), 3/4 inch (∼19.05 mm), 1 inch

Conclusion

In summary, we have demonstrated that over 1 kg Mg3.1Sb1.5Bi0.49Te0.01 powder can be prepared in a single batch using a Simoloyer ball-miller. Bulk Mg3.1Sb1.5Bi0.49Te0.01 samples with different diameters were successfully prepared using the hot-pressing method under proper conditions, and all of the samples show comparable thermoelectric performance. Scanning voltage probing and thermoelectric characterization also demonstrate that the as-prepared 2-inch-diameter sample is highly uniform. The

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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    These authors contributed equally to this work.

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