Superconductivity and crystal structure of the solid solutions of Ba8−δSi46−xGex (0?x?23) with Type I clathrate structure |
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Authors: | Hiroshi Fukuoka Junichi Kiyoto Shoji Yamanaka |
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Institution: | Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan |
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Abstract: | The solid solutions of barium containing Type I clathrate, Ba8−δSi46−xGex (0?x?23) were prepared under high-pressure and high-temperature conditions of 3 GPa at 800°C. All the solid solutions showed superconductivity, and the transition temperature (Tc) decreased from 8.0 to 2.0 K as the germanium content increased from x=0 to 23 in Ba8−δSi46−xGex. The single crystals with five different compositions were obtained and the structures, compositions, and site occupancies were determined from X-ray single-crystal analysis. A slight barium deficiency was observed at Ba1 (2a) sites for all the clathrates. The Ge atoms replaced the Si atoms at the Si3 (24k) site in the composition range of x<8, and then at the Si2 (16i) site. The crystals had a slight deficiency in the covalent (Si, Ge) network and the deficiency increased with the increase of the Ge content. |
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Keywords: | Silicon clathrate Superconductivity Superconductor Type I clathrate Single-crystal analysis |
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