Jpn. J. Appl. Phys. 39 (2000) pp. L1127-L1129 |Next Article| |Table of Contents|
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Express Letter
An Oxide Single Crystal with High Thermoelectric Performance in Air
Ryoji Funahashi,
Ichiro Matsubara,
Hiroshi Ikuta1,
Tsunehiro Takeuchi2,
Uichiro Mizutani2 and
Satoshi Sodeoka
Osaka National Research Institute, AIST, Midorigaoka, Ikeda, Osaka 563-8577, Japan
1Center for Integrated Research in Science and Engineering, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
2Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
(Received September 27, 2000; accepted for publication October 6, 2000)
An oxide single-crystalline whisker with high thermoelectric properties at temperatures (T) higher than 600 K in air has been discovered. This whisker is assigned to Ca2Co2O5 phase (abbreviated to Co-225 whiskers) and has a layered structure in which Co–O layers of two different kinds alternate in the direction of the c-axis. Seebeck coefficient of the whiskers is higher than 100 µV·K-1 at 100 K and increases with temperature up to 210 µV·K-1. Temperature dependence of electric resistivity shows a semiconducting-like behavior. These results indicate that the electric carriers are transported via hopping conduction. Using thermal conductivity of a Co-225 polycrystalline sample, figure of merit (ZT) of the Co-225 whiskers is estimated 1.2–2.7 at T≥873 K. This compound is characterized with regard to low mobility and high density of carriers, which contradicts the conventional materials with high thermoelectric properties.
URL:
http://jjap.jsap.jp/link?JJAP/39/L1127/
DOI: 10.1143/JJAP.39.L1127
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