Thermoelectric Properties of Doped Half-Heuslers NbCoSn1-xSbx and Nb0.99Ti0.01CoSn1-xSbx

概要

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The thermoelectric properties of doped half-Heuslers, NbCoSn1-xSbx and Nb0.99Ti0.01CoSn1-xSbx, have been studied in the temperature range from 320 to 850 K. These half-Heuslers are synthesized by the arc melting of pure metals followed by annealing for one week at 1123 K in vacuum. The samples with $x=0$, 0.02, 0.04, 0.06, 0.08, and 0.10 are prepared by spark plasma sintering (SPS) using fine powders of crushed arc-melted buttons. The sintered samples are of a nearly single phase. All the samples exhibit metal-like temperature-dependent electrical resistivity $\rho$ of the order of $10^{-6}$–$10^{-5}$ $\Omega$$\cdot$m in the measured temperature range. For both NbCoSn1-xSbx and Nb0.99Ti0.01CoSn1-xSbx, the $\rho$ values at 320 K rapidly decrease by partial substitution in the range between $x=0$ and 0.02, and finally reach 5 μ$\Omega$$\cdot$m at $x=0.10$. The Seebeck coefficient $S$ is appreciably enhanced by partly substituting Nb sites with 1 at. % Ti. The highest power factor is $22\times 10^{-4}$ W$\cdot$m-1$\cdot$K-2 for Nb0.99Ti0.01CoSn0.9Sb0.1 at 700 K. The thermal conductivity $\kappa$ weakly depends on temperature and does not show any peculiar trend upon Sb partial substitution. The dimensionless figure of merit $ZT=S^{2}T/\rho\kappa$ for Nb0.99Ti0.01CoSn0.9Sb0.1 reaches 0.3 at 850 K, which is fourfold that of pure NbCoSn.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-11-15