Output Power Characteristics of Mg 2 Si and the Fabrication of a Mg 2 Si TE Module with a Unileg Structure
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1166-N03-17
Output power characteristics of Mg2Si and the fabrication of a Mg2Si TE module with a uni-leg structure Takashi Nemoto1, Tsutomu Iida2, Yohei Oguni2, Junichi Sato1, Atsunobu Matsumoto2, Tatsuya Sakamoto2, Takahiro Miyata2, Tadao Nakajima1 Hirohisa Taguchi2, Keishi Nishio2 and Yoshifumi Takanashi2 1
Nippon Thermostat Co., Ltd., 6-59-2 Nakazato, Kiyose-shi, Tokyo 204-0003, Japan Department of Materials Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan
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ABSTRACT Mg2Si elements and a TE module with a transition metal electrode consisting of Ni were fabricated using a monobloc sintering. In order to design a structure for a thermoelectric module using Mg2Si, we examined the correlation between the ZT values and the power-output of a single element, using Mg2Si and Mg2Si doped with donor impurities, such as Al and/or Bi. The observed power-outputs for single elements of Mg2Si (ZT = 0.6), 2 at. % Bi-doped Mg2Si (ZT = 0.65) and 1at. % Bi + 1at. % Al-doped Mg2Si (ZT = 0.77) were 23.2 mW, 13.6mW and 19.4 mW at ΔT = 500 K (between 873 K and 373 K), respectively. Additionally, we developed and evaluated a new architecture, based on a ‘uni-leg’ structure Mg2Si TE power generation module. The observed maximum values for open circuit voltage (Voc) and output power (P) of the Mg2Si TE power generation module were 109 mV and 48 mW at ΔT = 500 K (between 873 K and 373 K), respectively. INTRODUCTION Thermal-to-electric (TE) energy conversion from waste heat source is a viable technology that can be instrumental in improving the potential conversion efficiency of caloric power generation, such as conventional heat engines and high temperature furnaces [1]. Magnesium silicide (Mg2Si) has been identified as a promising advanced thermoelectric material, operating in temperatures ranging from 500 to 800 K, because Mg2Si possesses essential requisites for achieving practical use, such as abundance of its constituent elements in the earth’s crust and non-toxicity of its processing-by-products [2-9]. Additionally, the dimensionless figure of merit, ZT, characterizing the efficiency of a thermoelectric material, of n-type Mg2Si has already reached ~1.0 at 873 K [10]. However, the correlation between the ZT values and the power generation characteristics, essential to the understanding of the design of a structure for a TE power generation module, has not been sufficiently investigated. In this experiment, three different single elements, using undoped Mg2Si and Mg2Si doped with donor impurities such as Al and/or Bi, were fabricated, and the open circuit voltage (VOC), the output current (I ) and the output power (P) of the three different elements were measured and compared. In addition this, we studied the relation of Seebeck coefficient and thermal conductivity to the value of VOC and the relation of electrical conductivity to the value of I. Additionally, as a feasible TE module, we developed a pin-fin structure TE module, which is the new architecture based on the uni-leg s
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