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Preparation of CaMgSi and Ca7Mg7.25Si14 single phase films and their thermoelectric properties

Published online by Cambridge University Press:  19 February 2019

Matsuo Uehara
Affiliation:
Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama226-8502, Japan.
Atsuo Katagiri
Affiliation:
Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama226-8502, Japan.
Mao Kurokawa
Affiliation:
Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama226-8502, Japan.
Kensuke Akiyama
Affiliation:
Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama226-8502, Japan. Kanagawa Institute of Industrial Science and Technology, Ebina, Kanagawa243-0435, Japan.
Takao Shimizu
Affiliation:
Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama226-8502, Japan.
Masaaki Matsushima
Affiliation:
Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama226-8502, Japan.
Hiroshi Uchida
Affiliation:
Department of Materials and Life Sciences, Sophia University, Tokyo102-8554, Japan.
Yoshisato Kimura
Affiliation:
Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama226-8502, Japan.
Hiroshi Funakubo*
Affiliation:
Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama226-8502, Japan.
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Abstract

Ca-Mg-Si films were firstly prepared on (001)Al2O3 substrates by RF-magnetron sputtering method from Mg disc target together with Ca and Si chips. The composition of the deposited films was controlled by adjusting deposition temperature and Ca/Si area ratio of Ca and Si chips on Mg disk target. Ca0.32Mg0.33Si0.35 film deposited at 610 K consisted of a single phase of CaMgSi and this CaMgSi phase was stable after heat treated at 770 K under an atmospheric Ar with 5% -H2. As-deposited film shows the semiconductor behavior and have a power factor of 50 μW/(mK2) at 670 K, while annealed one showed the metallic behavior and its power factor down below 10 μW/(mK2) at 320-770 K. On the other hand, Ca0.27Mg0. 51Si0.2 film deposited at 590 K showed no obvious crystalline phase but became single phase of Ca7Mg7.25Si14 after heat treatment at 770 K under an atmospheric Ar with 5% -H2. As deposited film had a large power factor of 100 μW/(mK2) at 670 K. However, power factor decreased below 1 μW/(mK2) at 320-770K after the heat treatment at 770 K under an atmospheric Ar with 5% -H2.

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Articles
Copyright
Copyright © Materials Research Society 2019 

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References

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