Preparation and thermoelectric properties of La filled skutterudites by mechanical alloying and hot pressing

Starting from elemental powder mixtures of LaxFe4Sb12 (x = 0.5, 1.0, 1.5), La filled skutterudites were prepared by mechanical alloying (MA) and hot pressing (HP), effect of La addition content on thermoelectric properties was studied in this paper. The as sintered samples were characterized by XRD, EDX and DTA. Owing to the incomplete filling of La, impurities such as Sb and FeSb2 manifest even at the La content of x = 1.0. Increasing the La addition to x = 1.5, the filled skutterudite phase overwhelms the impurities in the XRD pattern of the hot pressed sample. Over the temperature range of 300–750 K, the Seebeck coefficient and the electrical resistivity of the hot pressed samples increase with the increasing of both La addition and temperature. The thermal conductivity is greatly decreased in comparison with that of unfilled CoSb3 skutterudite. A maximum ZT of 0.41 was obtained at 750 K with a La content of x = 1.5.