Pressure induced phase transformation of semiconductor clathrates

Pressure induced phase transformation and amorphization for Ge-based type-I clathrates have been investigated by means of synchrotron XRD and Raman experiments under high pressure. The XRD results of Sr8Ga16Ge30, Ba8Ga16Ge30, and I8Sb8Ge38 demonstrated volume collapse phase transitions at 18, 33, and 42 GPa, respectively. Reitveld analyses performed for I8Sb8Ge38 reveal a deformation of six-member rings of 14-hedron cages with increasing pressure.