Study On Growth And Characterization Of High-quality Large Cubic Gem Diamond Crystals

Like other morphology with high-quality diamond crystal, high quality cubic hexahedral diamond crystals, is a kind of extensive materials, being widely used for industry, science, defense, medical field and other fields. In addition, hexahedral crystal also has its own unique function, particularly used as single crystal diamond tool and the crystal substrate of the synthesis diamond single by CVD. But the growth zone of hexahedral cubic crystal is very narrow, only about 10℃, and at a relatively low temperature region. So the crystal growth often tends to the high temperature region by temperature gradient method, and the synthesis of hexahedral crystals is relatively difficult.In this article, by temperature gradient method under HPHT, with self-made Fe_xNi_yCo_z alloy solvent and a new a%ZrO₂+b%MgO+c%MgCaCO₃+d%AL₂O₃ composite materials assisted, through adjusting the process of assembling and synthesis appropriately, Successfully synthesized high-quality hexahedral cubic large diamond crystals. In addition, we synthesized diamond crystals with NiMnCo and FeNi alloy solvent and the common ZrO₂+20% MgO materials. In order to compare with the performance of the high-quality hexahedral cubic large diamond crystals, such as the growth zone of the crystals, crystal color, quality, growth rate, and so on.Through comparison, we found a V-zone region of diamond growth with the catalyst of NiMnCo, it is easy to synthesize the skeletal crystals and excessive spontaneous nuclear. With the new materials , the fastest growth rate to 3.6mg/h; the catalyst of FeNi adapt to growth diamond crystal which has the shape of octahedral in the V-zone region of middle-temperature region, the fastest growth rate of high-quality crystals up to 6.2mg/h; The Fe_xNi_yCo_z catalyst increased the growth temperature is about 20℃in the V-zone of low-temperature region. And it can synthesized very high-quality hexahedral diamond crystals of weight about 2.0ct in a short time, which the growth rate could be increased to 7.8mg/h.Through compared with the growth rate with the sample of the Sumitomo Electric found that growth 1 carat weight of crystal by a small seed Sumitomo Corporation of Japan needs 64 hours, but our only 27 hours. It can be seen that the crystal growth rate is much higher than Japan's Sumitomo in this study.We made an in-depth study on the surface features of the crystal, quality, nitrogen content by High Optical micrographs, Raman spectroscopy and infrared absorption microscopy, which compared with Sumitomo Electric and Element Six, respectively. High Optical micrographs show that the crystal surface is very smooth after processed. The crystal's color distribution of the oars is better than Sumitomo Electric and Element Six. There are processed traces of the three samples'surface. The Raman spectroscopies of three diamonds were found that the FWHM values of Sumitomo Electric's samples is 5.298cm^-1, it less than the other's. It was show that the Sumitomo Electric's samples have a more perfect lattice. The infrared absorption microscopy spectra of diamonds were found that the crystals contain nitrogen concentration in our samples is 240 at.ppm, which are higher than Sumitomo Electric's samples and Element Six because the growth rate is too fast.