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.