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Doping Characteristics of Silver in Mg2Si1-xGex Prepared by Plasma Activated Sintering

Published online by Cambridge University Press:  01 February 2011

Takashi Nemoto
Affiliation:
tnemoto@ntcl.co.jp, Nippon Thermostat Co., Ltd, R&D Dept, 6-59-2 Nakazato, Kiyose-shi Tokyo, 204-0003, Japan
Junichi Sato
Affiliation:
j-sato@ntcl.co.jp, Nippon Thermostat Co., Ltd., 6-59-2 Nakazato, Kiyose-shi, Tokyo, 204-0003, Japan
Tsutomu Iida
Affiliation:
tsutomu@rs.noda.tus.ac.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Masayasu Akasaka
Affiliation:
m_akasak@rs.noda.tus.ac.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Atsunobu Matsumoto
Affiliation:
tnemoto@ntcl.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Tadao Nakajima
Affiliation:
tnemoto@ntcl.co.jp, Nippon Thermostat Co., Ltd., 6-59-2 Nakazato, Kiyose-shi, Tokyo, 204-0003, Japan
Keishi Nishio
Affiliation:
tnemoto@ntcl.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Yoshifumi Takanashi
Affiliation:
tnemoto@ntcl.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
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Abstract

Silver (Ag) doped Mg2Si1-xGex (x=0.1 to 0.4) samples were fabricated using a plasma activated sintering (PAS) method. The doping concentration of Ag was varied from 1 to 5 at.%. Undoped Mg2Si1-xGex exhibits n-type conductivity due to residual impurities in the Mg source material used and unintentionally process-induced impurities. The observed unstable behavior of the Seebeck coefficient of Ag-doped p-type Mg2Si1-xGex (x ≤ 0.3) in the region of 550 to 650 K, exhibiting a considerable drop in the value and occasional conduction type conversion, was correlated with the specific contaminants. For x∼0.4, the observed Seebeck coefficient varied from 0.2 mV/K at 823 K to 0.4 mV/K at room temperature, with no remarkable drop in the value with increasing temperature. An estimated ZT value of 5 at.% Ag doped Mg2Si0.6Ge0.4 was 0.18 at 844 K. It was found that both specific residual impurities and process-induced impurities affected the characteristics of the Seebeck coefficient of Mg2Si1-xGex.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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