| Abstract
| - Single crystals of the Ba-containing silicon clathrate superconductor Ba7.76Si46 were prepared using a high-pressureand high-temperature condition (3 GPa, 1300 °C). It crystallized in the cubic space group Pm-3n with a = 10.3141(7)Å and Z = 1. There are two crystallographically different types of Ba sites, at the centers of Si dodecahederal(Ba@Si20) and Si tetrakaidecahedral (Ba@Si24) cages. On evacuation at 527 °C, a part of Ba atoms were removedfrom the Ba@Si20 sites. The superconducting transition temperature (Tc) decreased from 9.0 to 6.0 K with thedecrease of the Ba content from 7.76 to 6.63 Ba/Si46. The Ba deficient sites and the deficiency were determinedby the structural refinement in the single-crystal X-ray analyses.
- Single crystals of the Ba-containing silicon clathrate superconductor Ba7.76Si46 were prepared using high-pressure and high-temperature conditions (3 GPa, 1300 °C). It showed superconductivity with transition temperature (Tc) of 9.0 K. On evacuation at 527 °C, part of Ba atoms were topotactically removed and the composition changed to Ba6.63Si46. The Tc decreased from 9.0 to 6.0 K with the decrease of the Ba content from 7.76 to 6.63 Ba/Si46.
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