Synthesis and crystal structure of CaxCo4Sb12 skutterudites

Abstract New skutterudite compounds Ca x Co 4 Sb 12 (0 x ⩽0.2) have been prepared by traditional metallurgical synthesis. The compounds have been characterized by X-ray powder diffraction (XRD), electron probe microanalysis (EPMA) and neutron powder diffraction. Rietveld refinement of the structures against neutron powder diffraction data (on Ca 0.1 Co 4 Sb 12 , Im 3 , a =9.0429 A, χ 2 =1.55; wR p =1.52) enabled the location of Ca in the voids of the skutterudite structure to be verified. The large displacement ellipsoid for Ca is consistent with “rattling” in the cage of the crystalline structure. XRD combined with EPMA analyses showed that the maximum occupancy of Ca atoms is about 0.2.