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HOME > No.8, Feb 2017 > Research Highlights : Development of a new thermoelectric material for a sustainable society

Development of a new thermoelectric material for a sustainable society

The first synthesis of bulk CaMgSi with thermoelectric properties.By Yoshikazu Todaka
Professor Todaka(left) with his students

Yoshikazu Todaka and his colleagues, in cooperation with researchers at the Nagoya Institute of Technology, have developed a new thermoelectric material, Calcium-Magnesium-Silicide (CaMgSi), which consists of non-toxic, cheap, and lightweight elements.

These findings could contribute to the development of green energy technology.

Thermoelectric materials, which can directly convert thermal energy into electrical energy (Seebeck effect), can be effectively used for the development of a clean and environmentally compatible power-generation technology.

However, these materials are not commonly used for practical applications as they mostly include toxic and/or expensive elements.

Recently, Professor Yoshikazu Todaka and his research group from Toyohashi University of Technology’s Materials Function Control Laboratory and the Nagoya Institute of Technology have successfully synthesized a new thermoelectric material, CaMgSi, which is an intermetallic compound. The key to this development was the synthesis procedure; bulk CaMgSi intermetallic compound was synthesized by combining mechanical ball-milling (MM) and pulse current sintering (PCS) processes.

Picture of the synthesized bulk CaMgSi thermoelectric material through the procedure developed in this study.

"Significant thermoelectric properties in the intermetallic compound, CaMgSi, have been predicted by both theoretical and experimental studies”, explain the researchers of this work, Nobufumi Miyazaki and Nozomu Adachi. " However, the biggest issue in front of us was the synthesis of thermoelectric CaMgSi of optimal size ", they continued. In general, alloys are produced by mixing the constituent elements in their molten forms. However, Mg vapors when the temperature is raised up to the melting temperature of Si; Ca, Mg, and Si can no longer exist in their liquid states.

Yoshikazu Todaka says "To overcome the aforementioned problem, we chose the mechanical ball milling process to mix the elements homogeneously, without melting, and then a chemical reaction between Ca, Mg, and Si was induced using the pulse current sintering process".

Figure 2.
Schematic illustration of the atomic structure of the synthesized CaMgSi determined by X-ray diffraction.

Consequently, it became possible to synthesize the intermetallic compound, CaMgSi, on a sufficient scale. The thermoelectric property of the synthesized CaMgSi exhibited a performance comparable to that of the previously developed Mg-based thermoelectric materials. It is expected that the slight change in the composition of CaMgSi and the addition of a fourth element to CaMgSi will further enhance its thermoelectric properties. Interestingly, they found that the novel thermoelectric material can exhibit both n- and p-type conductivity. Such a property is very significant for the application of such material in power-generation modules.

The new thermoelectric material synthesized in this study is composed of lightweight elements, and has a low density of 2.2 g/cm3. Therefore, one of the possible applications of the material is in automobiles to utilize waste heat emitted from engines. These findings could contribute to the development of green energy technology.

This study was supported by Iketani Science and Technology Foundation (Grant No. 0271039-A). A part of this study was performed at the BL02B2 beamline of the SPring-8 synchrotron radiation facility with the approval of the Japan Synchrotron Radiation Research Institute (Proposal No. 2014B1237).


Nobufumi Miyazaki, Nozomu Adachi, Yoshikazu Todaka, Hidetoshi Miyazaki, and Yoichi Nishino (2017). Thermoelectric property of bulk CaMgSi intermetallic compounds, Journal of Alloys and Compounds, 691, 914-918. 10.1016/j.jallcom.2016.08.227









本研究は、公益財団法人 池谷科学技術振興財団(Grant No. 0271039-A)の助成を受けて行われました。また、本研究の一部はSPring-8, BL02B2(課題番号2014B1237)にて実施されました。

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Researcher Profile

Yoshikazu Todaka
Name Yoshikazu Todaka
Affiliation Department of Mechanical Engineering
Title Professor
Fields of Research Physical Metallurgy