Low thermal conductivity in La-filled cobalt antimonide skutterudites with an inhomogeneous filling factor prepared under high-pressure conditions

La-filled skutterudites La x Co 4 Sb 12 ( x = 0.25 and 0.5) have been synthesized and sintered in one step under high-pressure conditions at 3.5 GPa in a piston-cylinder hydrostatic press. The structural properties of the reaction products were characterized by synchrotron X-ray powder diffraction,...

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Published inJournal of materials chemistry. A, Materials for energy and sustainability Vol. 6; no. 1; pp. 118 - 126
Main Authors Serrano-Sánchez, F., Prado-Gonjal, J., Nemes, N. M., Biskup, N., Varela, M., Dura, O. J., Martínez, J. L., Fernández-Díaz, M. T., Fauth, F., Alonso, J. A.
Format Journal Article
LanguageEnglish
Published Cambridge Royal Society of Chemistry 01.01.2018
Subjects
Carrier density
Cobalt
Current carriers
Cylinders
Diffraction
Electron microscopy
Heat conductivity
Heat transfer
Lanthanum
Phonons
Power factor
Pressure
Reaction products
Scattering
Sintering (powder metallurgy)
Thermal conductivity
Transmission electron microscopy
X ray powder diffraction
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Summary:La-filled skutterudites La x Co 4 Sb 12 ( x = 0.25 and 0.5) have been synthesized and sintered in one step under high-pressure conditions at 3.5 GPa in a piston-cylinder hydrostatic press. The structural properties of the reaction products were characterized by synchrotron X-ray powder diffraction, clearly showing an uneven filling factor of the skutterudite phases, confirmed by transmission electron microscopy. The non-homogeneous distribution of La filling atoms is adequate to produce a significant decrease in lattice thermal conductivity, mainly due to strain field scattering of high-energy phonons. Furthermore, the lanthanum filler primarily acts as an Einstein-like vibrational mode having a strong impact on the phonon scattering. Extra-low thermal conductivity values of 2.39 W m −1 K −1 and 1.30 W m −1 K −1 are measured for La 0.25 Co 4 Sb 12 and La 0.5 Co 4 Sb 12 nominal compositions at 780 K, respectively. Besides this, lanthanum atoms have contributed to increase the charge carrier concentration in the samples. In the case of La 0.25 Co 4 Sb 12 , there is an enhancement of the power factor and an improvement of the thermoelectric properties.
ISSN:2050-7488
2050-7496
DOI:10.1039/C7TA08545A