Synthesis and thermoelectric properties ofp-type barium-filled skutterudite Ba_yFe_xCo_4−xSb₁₂

Single-phase barium-filled skutterudite compounds, Ba_yFe_xCo_4−xSb₁₂(x= 0 to 3.0, y = 0 to 0.7), were synthesized by a two-step solid-state reaction method. The maximum filling fraction of Ba (y_max) in Ba_yFe_xCo_4–xSb₁₂increased with increasing Fe content and was found to be rather greater than that of Ce_yFe_xCo_4–xSb₁₂. They_maxvaried from 0.35 to near 1.0 when Fe content changed from 0 to 4.0. Ba_yFe_xCo_4–xSb₁₂showedp-type conduction at a composition range ofx= 0 to 3.0,y= 0 to 0.7. Carrier concentration and electrical conductivity increased with increasing Fe content and decreased with increasing Ba filling fraction. The Seebeck coefficient increased with increasing Ba filling fraction and with decreasing Fe content. Lattice thermal conductivity decreased with increasing Ba filling fraction and reached a minimum at a certain Ba filling fraction (y= 0.3 to 0.4). The greatestZTvalue of 0.9 was obtained at 750 K forp-type Ba_0.27Fe_0.98Co_3.02Sb₁₂. It is expected that further investigation on the optimization of filling fraction would result in a higherZTvalue at the moderately low Fe content region.