Effect of phonon scattering mechanisms on the lattice thermal conductivity of skutterudite-related compound
Yang Lei (杨磊), Wu Jian-Sheng (吴建生), Zhang Lan-Ting (张澜庭)
Key Laboratory of the Ministry of Education for High Temperature Materials and Testing, School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200030, China
Abstract We have prepared the skutterudite-related compounds FeCo$_3$Sb$_{12}$ and La$_{0.75}$Fe$_3$CoSb$_{12}$ with different average grain sizes (about 0.8 and 3.9μm) by hot pressing. Samples were characterized by XRD, EPMA and SEM. The lattice thermal conductivity was investigated in the temperature range from room temperature to 200℃. Based on the Debye model, we analyse the change in lattice thermal conductivity due to various phonon scattering mechanisms by examining the relationship between the weighted phonon relaxation time $\tau(\omega/\omega_{\rm D})^2$ and the reduced phonon frequency $\omega/\omega_{\rm D}$. The effect of grain boundary scattering to phonon is negligible within the range of grain sizes considered in this study. The large reduction in lattice thermal conductivity of FeCo$_3$Sb$_{12}$ compound contributes to the electron－phonon scattering. As for La$_{0.75}$Fe$_3$CoSb$_{12}$ compound, the atoms of La filled into the large voids in the structure of the skutterudite produce more significant electron－phonon scattering as well as more substitute of Fe at Co site at the same time. Moreover, the point-defect scattering appears due to the difference between the atoms of La and the void. In addition, the scattering by the rattling of the rare-earth atoms in the void is another major contribution to the reduced lattice thermal conductivity. Introducing the coupling of the electron－phonon scattering with the point-defect scattering and the scattering by the rattling of the rare-earth atom is an effective method to reduce the lattice thermal conductivity of the skutterudite-related compounds by substitution of Fe for Co and the atoms of La filled in the large voids in the skutterudite structure.
Received: 28 July 2003
Revised: 04 November 2003
Accepted manuscript online:
PACS:
81.20.Ev
(Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation)
(Scattering by phonons, magnons, and other nonlocalized excitations)
Fund: Project supported by the National Natural Science Foundation of China (Grant No 59902003).
Cite this article:
Yang Lei (杨磊), Wu Jian-Sheng (吴建生), Zhang Lan-Ting (张澜庭) Effect of phonon scattering mechanisms on the lattice thermal conductivity of skutterudite-related compound 2004 Chinese Physics 13 516
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