HARD DISORDERED PHASES PRODUCED AT HIGH-PRESSURE-HIGH-TEMPERATURE TREATMENT OF C-60

X-ray diffraction, hardness, conductivity, Raman and infrared studies of solid C-60 subjected simultaneously to high pressure at 8 GPa and t emperatures up to 1820 K have been carried out. A hard disordered stat e is formed at temperatures higher than 920 K and a cross-linked layer ed structure is proposed for this state. Crystalline phases obtained a t 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 spect ra of the disordered phase are interpreted as a collapse of the C-60 c ages and formation of an amorphous structure. The 3-D polymerization o f solid C-60 at high-pressure-high-temperature treatment is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.