Preparation and thermoelectric properties of La filled Fe-based Skutterudites compounds

Starting from element La, Fe and Sb powders, nominal LaxFe4Sb12 (x = 0.5, 1.0, 1.5) filled Skutterudite was prepared by mechanical alloying (MA), hot pressing (HP) and annealing, the effect of the La filling fraction on phase formation and thermoelectric properties of the hot pressed and the annealed samples was studied in this paper. It was found that quite a lot of Sb and FeSb2 peaks manifest in the XRD patterns of x = 0.5 and x = 1.0. Increasing the La addition to x = 1.5, almost single phase filled skutterudite is achieved and only minute traces of Sb and FeSb2 remain in the XRD pattern. The secondary phases such as Sb and FeSb2 almost e-liminated in the XRD pattern when the hot pressed La1. 5Fe4Sb12 sample was annealed at 650°C for 48h. Over the temperature range of 300-750K, the Seebeck coefficient and the electrical resistivity of the samples increase with 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 0.51 was obtained for the annealed La1.5Fe4Sb12 sample at 750K.