Shock-Wave Synthesis and HTHP Sintering of Cubic Silicon Nitride

The shock synthesis of cubic silicon nitride (c-Si$_{3}$N$_{4})$ was realized in a flat recovery container. Initial samples were pressed mix of $\beta $-Si$_{3}$N$_{4}$ and copper powders. At fraction of copper more than 60~vol.~{\%} and shock pressure about 53 GPa in ampoule cover the yield of a high-pressure phase reaches 95-100~{\%}. About compaction or sintering of c-Si$_{3}$N$_{4}$ powder to bulk it is not known. The explosive compaction and static HTHP sintering at pressure 5-6 GPa and temperature 1100$^{\circ}$C were used to form the bulks from this nano-dispersive material. The bulks up to 6-8 mm in size were obtained. Vickers hardness of the bulks reaches HV=31 GPa at indentation force of 200 g, that is more than hardness for cubic silicon nitride bulks obtained in diamond anvils by the other researchers (Tanaka, et al., 2002).