Thermoelectric Properties of Sb-doped Sintered Mg2Si Fabricated using Commercial Polycrystalline Sources
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1166-N03-21
Thermoelectric properties of Sb-doped sintered Mg2Si fabricated using commercial polycrystalline sources Naoki Fukushima1, Tsutomu Iida1, Masayasu Akasaka2, Takashi Nemoto3, Tatsuya Sakamoto1, Ryo Kobayashi1, Hirohisa Taguchi1, Keishi Nishio1 and Yoshifumi Takanashi1 1
Department of Materials Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan 2 Dow Corning Toray Co., Ltd., 2-2 Chigusa-Kaigan Ichihara City, Chiba 299-0108, Japan 3 Nippon Thermostat Co., Ltd., 6-59-2 Nakazato, Kiyose-shi, Tokyo 204-0003, Japan ABSTRACT
The thermoelectric (TE) properties, such as the Seebeck coefficient, the electrical and thermal conductivities, and the output power, of Sb-doped n-type Mg2Si were studied. A commercial polycrystalline source was used for the source material for the Mg2Si. TE elements with Ni electrodes were fabricated by using a monobloc plasma-activated sintering (PAS) technique. Compared with undoped samples, the ZT values of the Sb-doped samples were higher over the whole temperature range in which measurements were made; the maximum value for the Sb doped Mg2Si was 0.72 at 864 K. The TE characteristics of Sb-doped samples were found to be comparable to those of Bi-doped ones, and no significant difference in ZT value was observed between them. Provisional results showed that the maximum value of the output power was 6.75 mW for the undoped sample, 4.55 mW for a 0.5 at% Sb doped sample, and 5.25 mW for a 1 at% Sb doped sample with ∆T = 500 K (between 873 K and 373 K). INTRODUCTION Magnesium silicide (Mg2Si) has been identified as a well-balanced thermoelectric material that covers the temperature range from 500 to 800 K[1-2], and one that fits well with the operating temperatures of industrial furnaces, automobile exhausts, and incinerators. The important features of Mg2Si include the fact that it has been identified as an environmentally-benign material, that its constituent elements are abundant in the earth’s crust, and that it is non-toxic[3-5]. Although thermoelectric devices have obvious merits in terms of power generation, one of the reasons why thermoelectric devices are not more widely used at present is that the cost-per-watt of thermoelectric power generation has been too high to allow it to displace existing technologies. Mg2Si has significant advantages for various applications in terms of both lower raw materials costs due to the abundance of its constituent elements, and its lighter weight compared with conventional thermoelectric materials such as Bi2Te3 and CoSb3. In order to optimize the thermoelectric properties of Mg2Si for practical applications, it needs to be doped, and typical device operating temperatures require that any substitutional element used as a dopant be highly stable. Stable dopant elements in Mg2Si are needed to ensure long lifetime operation at elevated temperatures. Aluminum (Al), bismuth (Bi) and antimony (Sb) are well known n-type dopants for Mg2Si. Calculations from first principles show that Sb is the most stab
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