Substantial thermal conductivity reduction in mischmetal skutterudites MmxCo4Sb12 prepared under high-pressure conditions, due to uneven distribution of the rare-earth elements

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 7; no. 14; pp. 4124 - 4131
• Main Authors: Gainza, J, Serrano-Sánchez, F, Prado-Gonjal, J, Nemes, N M, Biskup, N, Dura, O J, Martínez, J L, Fauth, F, Alonso, J A
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2019
• Subjects: Cylinders; Diffraction patterns; Eels; Heat conductivity; Heat transfer; High temperature; Mischmetal; Phonons; Power factor; Rare earth elements; Stress concentration; Synchrotron radiation; Synthesis; Thermal conductivity; X-ray diffraction
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c8tc06461j

Thermoelectric mischmetal-filled MmxCo4Sb12 (Mm: natural cocktail of rare-earth elements, mostly Ce and La) skutterudites have been synthesized and sintered in one step under high-pressure conditions at 3.5 GPa in a piston–cylinder hydrostatic press. Synchrotron X-ray diffraction patterns display a splitting of the diffraction peaks ascribed to purely Ce-, and Mm-filled skutterudite phases, which have been analyzed and confirmed by high-resolution TEM and EELS. A total thermal conductivity (κ) of 1.51 W m−1 K−1 is measured at 773 K for Mm0.5Co4Sb12, below that of other filled skutterudites, which is promoted by the enhanced phonon scattering over a broad range of the phonon spectrum due to the inhomogeneous and nanoscale mischmetal inclusion. Compared to undoped CoSb3 skutterudite synthesized by conventional methods, κ is reduced by a factor of 3, while the power factor is also substantially enhanced.