2005 Volume 60 Issue 7 Pages 543-546
Silicon clathrates are covalent bonded cage-like crystals composed of face-sharing Si20, Si24, and Si28 polyhedra in which guest atoms are occupied. These compounds continue to attract much attention as new superconductors, unusual wide-bandgap semiconductor, and a new class of thermo-electric materials. Vibrational properties of guests and host lattice, and the guest-host interactions are studied by high-pressure Raman spectroscopy. By considering these results and high-pressure phase transitions of Si clathrates, we investigate their characteristics depending on guests and cage-structures.