Gemmological Characteristic and Comparison of CVD Synthetic Diamond from Chinese Company and Foreign Company

In recent years, the production and technology of CVD synthetic diamonds in China have developed rapidly. In this paper, the gemmological characteristics of CVD synthesis diamonds produced by Ningbo Crysdirm Industrial Technology Co.Ltd in 2017 were researched, and were compared with the CVD diamonds from Ⅱa company in Singapore. The CVD synthetic diamonds produced by Ningbo Crysdirm has the same conventional gemmological properties as natural diamonds. There are black polycrystalline diamond inclusions and lamellar structure in CVD synthetic diamond samples. Photoluminescence spectra showed that there are characteristic absorption peaks at 737, 637 nm and 575 nm in CVD synthetic diamond samples. Besides the characteristic peaks, CVD synthetic diamond produced by Ⅱ a company has additional characteristic peaks at 766, 659, 607 nm. It was revealed that there are differences in the process conditions of different manufacturers, which is of certain significance for the source tracing of CVD synthetic diamonds.In addition, for the microzone test in different regions of CVD synthetic diamond, the poor N impurity incorporation and the incomplete dehydrogenation of raw materials are the reasons for the poor crystallinity of CVD synthetic diamonds.