Enhancement of thermoelectric properties of Co4Sb12 Skutterudite by Al and La double filling

Abstract

This work reports the enhancement of thermoelectric properties of La0.5Co4Sb12 compound due to addition of Al. A polycrystalline AlxLa0.5Co4Sb12 (0 ​≤ ​x ​≤ ​0.5) skutterudites were successfully prepared by mechanical alloying and spark plasma sintering techniques. The characterization of phase structure and morphology of AlxLa0.5Co4Sb12 bulk samples are examined by XRD and SEM-EDX analysis. The results revealed that the main phase of CoSb3 skutterudite structure with a small amount of Al were distributed in the grain boundaries for the most of AlxLa0.5Co4Sb12 samples. The thermoelectric measurements of consolidated samples were evaluated from room temperature to 800 ​K. The electrical resistivity remarkably reduced through the addition of Al to the lowest value of 7.6 ​μΩm at room temperature for Al0.05La0.5Co4Sb12 sample. Moreover, the absolute Seebeck coefficient was significantly improved by Al addition and the highest value of 193 ​μV/K was observed at 789 ​K for Al0.05La0.5Co4Sb12 sample. Furthermore, the same formulation showed a significant enhancement on the power factor that reached the maximum value of 4.02 ​× ​10−3 ​W/mK2 at 789 ​K. The thermal conductivity and lattice thermal conductivity were significantly minimized to the value of 1.1 ​W/mK (at 789 ​K) and 0.64 ​W/mK (at 595 ​K), respectively for Al0.3La0.5Co4Sb12 due to the enhancement of phonon scattering. Additionally, a comprehensive improvement on the dimensionless figure of merit value ZT of 1.36 for Al0.05La0.5Co4Sb12 at 789 ​K has been achieved.