Synthesis of diamonds in Fe—C systems using nitrogen and hydrogen co-doped impurities under HPHT

In this study, we investigate the effect of nitrogen and hydrogen impurities on colors, morphologies, impurity structures and synthesis conditions of diamond crystals in Fe-C systems with C₃N₆H₆ additives at pressures in the range 5.0-6.5 GPa and temperatures of 1400-1700 ℃ in detail. Our results reveal that the octahedron diamond nucleation in a Fe-C system is evidently inhibited by co-doped N-H elements, thereby resulting in the increase of minimum pressure and temperature of diamond synthesis by spontaneous nucleation. The octahedron diamond crystals synthesized from a pure Fe-C system are colorless, while they become green in the system with C₃N₆H₆ additive. The surface defects of diamond will deteriorate when the nitrogen and hydrogen atoms simultaneously incorporate in the diamond growth environment in the Fe-C system. We believe that this study will provide some important information and be beneficial for the deep understanding of the crystallization of diamonds from different component systems.