Synthesis of filled skutterudite compounds: Ba_yFe_xCo_4-xSb₁₂

Ba-filled skutterudite compounds, Ba_yFe_xCo_4-xSb₁₂, were synthesized by a two-step solid reaction method. A binary compound of Sb₃Ba and a ternary compound of Fe_xCo_1-xSb₂ were first synthesized at 900 and 973 K, respectively. The presynthesized Sb₃Ba and Fe_xCO_1-xSb₂ were then mixed with Sb and heated at 973 K in an Ar atmosphere. The resulting powder was of single phase with a composition of Ba_yFe_xCo_4-xSb₁₂, having skutterudite structure with the Sb-dodecahedron voids fractionally filled by Ba. The lattice constant of Ba_yFe_xCo_4-xSb₁₂ increased with Ba and Fe content. The maximum filling fraction of Ba (y_max) in Ba_yFe_xCo_4-xSb₁₂ was found to be greater than that of Ce or La in Ln_yFe_xCo_4-xSb₁₂, especially in the lower Fe content region. The y_max varied from 0.35 to near 1.0 when Fe content (x) changed from 0 to 4.