High-Pressure Synthesis and the Structure Refinement of CoSb3-Based Filled-Skutterudites

Various 14-group elements were inserted in the skutterudite-type CoSb3 host lattice under high-pressure and temperature conditions of 8 GPa and 550°C using the Belt-type high-pressure equipment. It was found that various elements could be inserted in the body-centered vacant site, resulting in the formation of new filled-skutterudites MxCo4Sb12 (M: Ge, Sn, Pb). The composition and the degree of space-filling were determined by the Rietveld analysis and the density measurements. Maximum space-filling was determined to be 50% for M=Ge, 100% for M=Sn, and 70% for M=Pb. The inserted Sn atom shows anomalous large thermal vibration amplitude, while Pb atom does not. The Ge atom locates the position slightly deviated from the ideal body-centered position.