Synthesis of filled skutterudite compounds: BayFexCo4−xSb12

Abstract
Ba-filled skutterudite compounds, BayFexCo4−xSb12, were synthesized by a two-step solid reaction method. A binary compound of Sb3Ba and a ternary compound of FexCo1−xSb2 were first synthesized at 900 and 973 K, respectively. The presynthesized Sb3Ba and FexCo1−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 BayFexCo4−xSb12, having skutterudite structure with the Sb–dodecahedron voids fractionally filled by Ba. The lattice constant of BayFexCo4−xSb12 increased with Ba and Fe content. The maximum filling fraction of Ba (ymax) in BayFexCo4−xSb12 was found to be greater than that of Ce or La in LnyFexCo4−xSb12, especially in the lower Fe content region. The ymax varied from 0.35 to near 1.0 when Fe content (x) changed from 0 to 4.