Lattice Thermal Conductivity of Co1-xFexSb3

We have investigated the effect of iron doping on the cobalt site for CoSb 3 skutterudite by measuring the lattice thermal conductivity from 2K to 300K. The doping levels of iron are 0, 0.5, 1, 2, 5, and 10 at%. Samples were prepared by induction melting of the constituents followed by annealing at 700 °C for 20 hours. The peak in the lattice thermal conductivity decreases as the iron doping level increases and is ultimately reduced by an order of magnitude for the sample with 10 at% iron. This is surprising because the mass and the size differences between iron and cobalt are only 5% and 6%, respectively. The reduction of thermal conductivity can be explained by the presence of lattice defects. Our theoretical model fits the temperature dependence of lattice thermal conductivity for all the samples very well. Magnetization measurements were performed to discern the charge state of Fe.