Influence of Aluminum Addition on Thermoelectric Performance of Mg 2 Si Compound under Air Exposure with Temperature Dif
- PDF / 2,650,936 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 57 Downloads / 207 Views
Influence of Aluminum Addition on Thermoelectric Performance of Mg2Si Compound under Air Exposure with Temperature Difference Takashi Itoh1 and Akira Tominaga1 1 Materials Science and Engineering, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8603, Japan ABSTRACT Dimagnesium silicide (Mg2Si) is an eco-friendly material useful for thermoelectric generation using waste heat of temperature range of 600 to 900 K. To improve the thermoelectric performance of the Mg2Si compound, we made the Al-added compounds under magnesium-rich condition (with 67.0 at% of Mg) using a liquid-solid phase reaction and using a pulse discharge sintering. The thermoelectric performance of each sample containing Al of 0 to 2.0 at% was measured during 50 h air exposure with temperature difference. The temperature difference was given by contacting the hot side of a sample with a hot plate kept at 773 K and by contacting the cold side with a heat sink with cooling fan. The electrical resistivity of the Al-free sample increased with air exposure time by internal oxidation. All the Al-added samples kept the low resistivity during the air exposure test. We confirmed the resistance to deterioration in thermoelectric performance of the Al-added samples during air exposure with temperature difference. INTRODUCTION Mg2Si is a promising n-type eco-friendly thermoelectric compound available for thermoelectric generation using waste heat of temperature range of 600 to 900 K. This material has advantages of low density below half of the usual thermoelectric materials, of abundance of its constituent elements in the Earth’s crust and of harmlessness of its processing by-products. For improvement of the thermoelectric properties, many researchers have been studied about the dopants of Mg2Si compound theoretically and experimentally[1-8]. The dopants (Al, P, Zn, Ga, Ag, Cd, In and Sb) in Mg2Si were investigated in their literatures. Among these elements, the Al element is known as one of the promising dopants that have a possibility for improving the thermoelectric performance of Mg2Si. Some experimental researches [7-9] reported with respect to the Al-added Mg2Si compounds and investigated their thermoelectric properties. However, the actual condition of thermoelectric performance in the Al-added Mg2Si compounds under the actual air exposure with temperature difference has not been sufficiently clarified, yet. In the present study, the Mg2Si samples with different Al content were prepared by the manufacturing process [10] that combines a liquid-solid phase reaction (LSPR) synthesis and a pulse discharge sintering (PDS). The change in thermoelectric performance with the passage of time was investigated under air exposure with temperature difference. EXPERIMENTAL DETAILS
For the synthesis of Al-free and Al-added Mg2Si compounds, the raw powders, that is, Mg (purity > 99.9 %, particle size < 180 μm), Si (> 99.9 %, < 75 μm) and Al (> 99.9 %, 106-180 μm) powders were used. They were supplied by KOJUNDO Chemical Laboratory Co., Japan. The Al powder with 0,
Data Loading...
