Abstract
La/Ce-partially double-filled and Co-charge-compensated (La1−zCez)0.8Fe4−xCoxSb12 skutterudites were synthesized, and their thermoelectric properties were studied by varying the filling ratio and charge compensation. X-ray diffraction analysis revealed that the matrix phase was skutterudite and a secondary phase was determined to the marcasite FeSb2. However, the formation of marcasite could be inhibited by increasing the Co content. Rare-earth antimonides, including LaSb2 and CeSb2, which were formed in fully filled La1−zCezFe4−xCoxSb12, were not found after La/Ce partial filling. La/Ce filling and Co substitution were confirmed by the decrease in lattice constants, from 0.9137 to 0.9099 nm, with increasing Ce and Co contents. Electrical conductivity showed negative temperature dependence, indicating metallic or degenerate semiconductor characteristics. Intrinsic conduction resulted in the maximum Seebeck coefficient at temperatures between 723 and 823 K. As the Co-substitution and Ce-filling contents increased, the Seebeck coefficient increased, while electrical and thermal conductivities decreased. This was considered to be due to difference in the valences of La<sup>3+</sup> and Ce<sup>3+/4+</sup> and the increase in carrier concentration caused by Co charge compensation. However, because they had similar atomic masses and ionic radii, the effects of the La/Ce filling ratio were not significant. Instead, Co charge compensation had the dominant effect on thermoelectric properties. The maximum Seebeck coefficient of 165.4 µVK<sup>-1</sup> was obtained for (La0.25Ce0.75)0.8Fe3CoSb12 at 823 K, and the highest electrical conductivity of 2.27 × 10<sup>5</sup> S m<sup>-1</sup> was achieved for (La0.75Ce0.25)0.8Fe4Sb12. (La0.25Ce0.75)0.8Fe3CoSb12 exhibited the lowest thermal conductivity of 2.15 W m<sup>-1</sup>K<sup>-1</sup> at 523 K and (La0.75Ce0.25)0.8Fe3.5Co0.5Sb12 showed the highest power factor of 2.53 mW m<sup>-1</sup> K<sup>-2</sup> at 723 K. The maximum dimensionless figure of merit, ZTmax = 0.71, was achieved at 723 K for (La0.75Ce0.25)0.8Fe3CoSb12.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
