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Effects of Sb-doping on electrical transport properties of Co-based half-Heusler compound

Published online by Cambridge University Press:  01 February 2011

Yasuhiro Ono ,
Shingo Inayama ,
Hideaki Adachi ,
Satoshi Yotsuhashi ,
Yuzuru Miyazaki  and
Tsuyoshi Kajitani
Yasuhiro Ono
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aobayama-05, Aoba-ku, Sendai, 980–8579, Japan.
Shingo Inayama
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aobayama-05, Aoba-ku, Sendai, 980–8579, Japan.
Hideaki Adachi
Affiliation:
Advanced Technology Research Laboratories, Matsushita Electric Industrial Co., LTD., 3–4 Hikaridai, Seika, Souraku, Kyoto, 619–0237, Japan
Satoshi Yotsuhashi
Affiliation:
Advanced Technology Research Laboratories, Matsushita Electric Industrial Co., LTD., 3–4 Hikaridai, Seika, Souraku, Kyoto, 619–0237, Japan
Yuzuru Miyazaki
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aobayama-05, Aoba-ku, Sendai, 980–8579, Japan.
Tsuyoshi Kajitani
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aobayama-05, Aoba-ku, Sendai, 980–8579, Japan.
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Abstract

Electrical transport properties of NbCoSn1−xSbx (x =0, 0.01, 0.02 and 0.05), a half-Heusler compound and its alloys, have been studied in the temperature range from 80 K to 850 K. As-prepared samples exhibit metallic conduction and similar Seebeck coefficients near 300 K (S = –100 μVK−1). Except for NbCoSn0.95Sn0.05, both electrical resistivity, ρ, and the absolute value of S appreciably increase during the annealing for 6 days at 1123 K. Unusual increase in ρ of the annealed NbCoSn sample is found at about 200 K. ρ-T curves of the other annealed samples remain metallic over the measured temperature range and the ρ value noticeably decreases with increasing Sb content, x. Among the annealed samples, the high power factor, 25×10−4 Wm−1K−2 at 850 K, is obtained for NbCoSn0.95Sb0.05. The band structure of NbCoSn is calculated based on the determined crystal structure, indicating that NbCoSn is an indirect transition-type semiconductor with a band gap of approximately 1 eV. This is not consistent with the metallic behavior of ρ observed for the annealed NbCoSn sample above 400 K. Partial disordering of Nb and Co atoms is a conceivable answer.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 793: Symposium S – Thermoelectric Materials 2003 - Research and Applications , 2003 , S8.5
Copyright
Copyright © Materials Research Society 2004

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