Hard disordered phases produced at high-pressure–high-temperature treatment of C60 Original Research Article

X-ray diffraction, hardness, conductivity, Raman and infrared studies of solid C60 subjected simultaneously to high pressure at 8 GPa and temperatures up to 1820 K have been carried out. A hard disordered state is formed at temperatures higher than 920 K and a cross-linked layered structure is proposed for this state. Crystalline phases obtained at T<920 K have a hardness near 1–2 GPa that rises strongly up to 38 GPa for disordered phases. The changes in the Raman and infrared spectra of the disordered phase are interpreted as a collapse of the C60 cages and formation of an amorphous structure. The 3-D polymerization of solid C60 at high-pressure–high-temperature treatment is discussed.