Thermoelectric properties of binary Cd-Yb quasicrystals and Cd6Yb

• Published in: Journal of applied physics 2004-02, Vol.95 (4), p.1900-1905
• Main Authors: Kuo, Y. K., Lai, J. R., Huang, C. H., Ku, W. C., Lue, C. S., Lin, S. T.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1642282

The thermoelectric properties, including electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) on binary icosahedral Cd-Yb quasicrystals and Cd6Yb are investigated. The Cd-Yb quasicrystals have a room-temperature (RT) resistivity value of about 200 (μΩ cm), however, the temperature-dependent resistivity is sensitive to a small composition change in these compounds. For all studied samples, Seebeck coefficients are positive and small (∼10 μV/K at RT). Upon cooling, S decreases quasilinearly, indicative of a metallic diffusion behavior, and then develops a broad phonon drag peak at around 40 K. The temperature characteristic of thermal conductivity κ of Cd-Yb quasicrystals shows a most peculiar feature in all measured thermoelectric properties. The RT κ value ∼6 (W/m K) of Cd-Yb quasicrystals is considerably larger than that of conventional ternary counterparts. Such an observation is attributed to the substantial electrical contribution κe (∼50%) to their total thermal conductivity, as deduced from the Wiedemann–Franz’s law, and larger lattice thermal conductivity κP due to less chemical disorder present in the binary Cd-Yb quasicrystalline structure. In addition κ decreases with decreasing temperature and shows a distinct maximum, a broad maximum, or a plateau at low temperatures, depending on the sample composition. The dimensionless thermoelectric figure of merit (ZT) for Cd-Yb quasicrystals is estimated to be small, on the order of 0.005 at RT.