Polymerization and phase diagram of solid C70 after high-pressure-high-temperature treatment

For the first time investigations of structure and physical properties of C-70 after treatment at 4 less than or equal to P less than or equal to 12.5 GPa and 300 less than or equal to T less than or equal to 1770 K were carried out by X-ray, Raman and infrared spectroscopy. The results are plotted in a (P,T) diagram. The new superhard 3D-polymerized tetragonal phase has been found at P greater than or equal to 9.5 GPa. The superhard disordered state of samples produced from C-70 at 12.5 GPa with a hardness close to that of (100)-face diamond has also been found. (C) 1998 Elsevier Science B.V.