Preparation and thermoelectric properties of LaxFeCo3Sb12 skutterudites by mechanical alloying and hot pressing

Single phase polycrystalline LaxFeCo3Sb12 (x = 0.2, 0.4, 0.6 and 0.9) skutterudites were successfully prepared by mechanical alloying (MA) and hot pressing (HP). Thermoelectric properties including the Seebeck coefficient, the electrical resistivity, the thermal conductivity and the dimensionless figure of merit ZT were discussed over the range 300–750 K. It was found that all samples showed p-type conduction. For x = 0.2, 0.4 and 0.6, the Seebeck coefficient increased gradually over the whole temperature range of measurements, however, the electrical resistivity was weakly temperature dependent and increased slightly with temperature. For x = 0.9, the Seebeck coefficient and the electrical resistivity increased with temperature and reached a maximum value at about 650 K and then decreases with temperature. The thermal conductivity was greatly decreased by filling rear-earth element La into the voids of skutterudite structure. As a result, the La0.4FeCo3Sb12 skutterudite exhibited a maximum figure of merit of 0.32 at about 750 K.