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Synthesizing and Subsequent Annealing of Si-based Thermoelectric Material Ba8AuxSi46-x Clathrates

Published online by Cambridge University Press:  25 October 2012

Bin Liu
Affiliation:
Department of Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
Makoto Saisho
Affiliation:
Department of Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
Yuya Nagatomo
Affiliation:
Department of Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
Mikihito Tajiri
Affiliation:
Department of Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
Yusuke Nakakohara
Affiliation:
Department of Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
Osamu Furukimi
Affiliation:
Department of Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
Ryo Teranishi
Affiliation:
Department of Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
Shinji Munetoh
Affiliation:
Department of Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
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Abstract

We prepared the type-I Ba8AuxSi46-x (x=5.5, 5.4 and 5.33) clathrates with p-type conduction by arc-melting and subsequent annealing. The Seebeck coefficients of all as-synthesized samples were negative. After annealing, in the case of x=5.4 and 5.5, the Seebeck coefficients changed to positive, and in the case of x=5.33, this value was negative for the annealed sample. The chemical composition revealed that Au content in the Ba8AuxSi46-x clathrates increased after the annealing process. The backscattered electron images showed that there were many Au-excess regions which were not clathrate structure in the as-synthesized samples, and these regions decreased and even disappeared after the annealing process. The disappearing of Au-excess regions can be explained by the diffusion of Au atoms from the Au-excess regions into the clathrates. Based on these results, annealing treatment can be used to tune the carrier conduction by controlling the content of Au for type-I Ba8AuxSi46-xclathrates.

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Articles
Copyright
Copyright © Materials Research Society 2012

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