Shock compression of C$_{70}$ fullerite with use of recovery assemblies

Shock-induced phase transitions of C$_{70}$ fullerite were studied with use of recovery assemblies of planar geometry. The starting material consisted of two crystalline phases: phase with hexagonal close-packed (hcp) and phase with rhombohedral structure. In the specimens, maximal shock pressures were reached after several reverberations of the waves between the walls of the recovery ampoule (step-like shock-wave compression) and were ranged from 9 to 52 GPa. We have found that C$_{70}$ fullerite undergoes a series of shock-induced polymorphic phase transitions. In the samples, recovered from 9, 14 and 19 GPa, a dominant phase was fullerite C$_{70}$ with cubic structure. Also, some amount of C$_{70}$ with hcp structure was observed. The quantity of hcp phase was decreasing with increasing of intensity of shock compression. With further growth of shock pressure, destruction of C$_{70}$ molecules occurs. In the specimens recovered after shock compression up to pressures over 19 GPa, the main phase was graphite with a low degree of three-dimensional regularity.