Synthesis and Thermoelectric Properties of (La1−zNdz)0.8Fe4−xCoxSb12 Skutterudites

Synthesis and Thermoelectric Properties of (La1−zNdz)0.8Fe4−xCoxSb12 Skutterudites

p-Type (La1−zNdz)0.8Fe4−xCoxSb12 skutterudites were prepared by partial double filling with La/Nd and charge compensation by substituting Co for Fe. The skutterudite phase was successfully synthesized using encapsulated melting, quenching, annealing and hot-pressing processes, but a small amount of the marcasite phase was identified. Partial filling within the filling fraction limit did not result in the formation of the (La,Nd)Sb2 phases detected in the fully-filled La1−zNdzFe4−xCoxSb12 because that phase is generated when the La/Nd partial filling exceeds the filling fraction limit. (La0.25Nd0.75)0.8Fe4Sb12 showed the highest electrical conductivity of 2.32 × 105 S m−1 at 323 K, and (La0.75Nd0.25)0.8Fe3CoSb12 exhibited the largest Seebeck coefficient of 167 μV K−1 at 723 K. The power factors and thermal conductivities of all the specimens were in the range of 1.43−2.59 mW m−1 K−2 and 2.05−3.95 W m−1 K−1, respectively, in the temperature range of 323−823 K. (La0.25Nd0.75)0.8Fe3CoSb12 showed the highest power factor of 2.59 mW m−1 K−2 at 823 K and the lowest thermal conductivity of 2.05 W m−1 K−1 at 323 K. Thus, (La0.25Nd0.75)0.8Fe3CoSb12 exhibited a maximum dimensionless figure of merit (ZT max) of 0.76 at 723 K.

p-Type (La1−zNdz)0.8Fe4−xCoxSb12 skutterudites were prepared by partial double filling with La/Nd and charge compensation by substituting Co for Fe. The skutterudite phase was successfully synthesized using encapsulated melting, quenching, annealing and hot-pressing processes, but a small amount of the marcasite phase was identified. Partial filling within the filling fraction limit did not result in the formation of the (La,Nd)Sb2 phases detected in the fully-filled La1−zNdzFe4−xCoxSb12 because that phase is generated when the La/Nd partial filling exceeds the filling fraction limit. (La0.25Nd0.75)0.8Fe4Sb12 showed the highest electrical conductivity of 2.32 × 105 S m−1 at 323 K, and (La0.75Nd0.25)0.8Fe3CoSb12 exhibited the largest Seebeck coefficient of 167 μV K−1 at 723 K. The power factors and thermal conductivities of all the specimens were in the range of 1.43−2.59 mW m−1 K−2 and 2.05−3.95 W m−1 K−1, respectively, in the temperature range of 323−823 K. (La0.25Nd0.75)0.8Fe3CoSb12 showed the highest power factor of 2.59 mW m−1 K−2 at 823 K and the lowest thermal conductivity of 2.05 W m−1 K−1 at 323 K. Thus, (La0.25Nd0.75)0.8Fe3CoSb12 exhibited a maximum dimensionless figure of merit (ZT max) of 0.76 at 723 K.