Synthesis and characterization of gem diamond single crystals in Fe-C system under high temperature and high pressure

Abstract

• High-quality gem diamond were successfully synthesized in the pure Fe-C system. • There are no NV 0 , NV − center in diamond synthesized in pure Fe-C system. • Our findings are greatly helpful for the synthetic high-purity diamond crystal. In this paper, the diamond large single crystals were successfully synthesized in the pure Fe-C system by temperature gradient growth (TGG) method in China-type cubic anvil high-pressure apparatus (CHPA) at 5.8 GPa and 1550 °C. The synthesized diamonds were characterized by Optical microscopy, Infrared spectroscopy, Raman spectroscopy and Photoluminescence (PL) spectroscopy. The results show that the nitrogen concentration of type Ib diamonds synthesized in pure Fe-C system is about 80 ppm, which is much lower than diamonds synthesized by Ni-based and Fe-based alloys. PL spectra result indicated that there were no peaks related to the NV centers in diamonds synthesized by Fe-C system. In addition, high-quality type IIa gem diamond can be synthesized by adding a small amount of nitrogen getter in the pure Fe-C system. We believe that this work is of great significance for the synthesis of high-purity large single type IIa diamonds without impurities such as nitrogen and metals.