High temperature thermoelectric properties of BaxYbyFe3CoSb12 p-type skutterudites

Double-filled high Fe content skutterudites, BaxYbyFe3CoSb12 (x + y = 1), were synthesized to investigate their high temperature transport properties. Both their phase and stoichiometry were characterized by powder x-ray diffraction and energy dispersive spectroscopy. The Seebeck coefficient, S, and electrical resistivity, q, increase with increasing temperature for all specimens over the entire measured temperature range. The thermal conductivity for the two low Ba content specimens decreases with increasing temperature up to 550 K at which point it increases with temperature due to bipolar diffusion. Bipolar diffusion becomes negligible with increasing Ba content. Due to this low bipolar diffusion, the ZT values of the higher Ba content specimens increase linearly with temperature, with the highest ZT value obtained for Ba0.9Yb0.1Fe3CoSb12.