Synthesis And Study Of S-doped Diamond Under High Temperature And High Pressure

Diamond is a representative production of superhard materials. It is a limiting functional material with many exceptional physical and chemical properties. Now, it has been applied in many fields such as industry, scientific research, national defense, medical treatment etc. Diamond plays an important part in the development of industry. China is not rich in natural diamond, so that independently holding high-level diamond synthesis technique is of realistic strategic significance.Natural diamonds are usually hosted by kimberlites and lamproites, which contain sulfur. Sulphides are the most common syngenetic inclusions in natural diamonds. Study on the influence of sulfur on diamond growth will contribute to understanding the formation of natural diamonds. This research will also be helpful to explore new type catalyst, and synthesize special type diamond.In this paper, by temperature gradient method (TGM), with NiMnCo and FeNi alloy as solvent catalysts, FeS(S) and boron as additives, the synthesis of large diamond crystals is investigated under high pressure and high temperature (HPHT) of about 5.4GPa and 1550K. We worked over the effect of diamond surface dangling bond on the morphology and quality of diamond, crystal growth rate and color of crystal.It was found that, when the content of FeS less then 1% in the single FeS-doping system, the color and the quality of diamond change a little; with the content of FeS in the growth system increased, the colors of grown crystals would be changed from transparent yellow to opaque gray-black, and the quality of diamond crystals would also be destroyed markedly, specialties in the (100) crystal face; with the content of FeS increased up to 1.75%, the (100) crystal face have been subjected to more serious dastroyed, while a lots of spontaneous nucleation of diamond appeared in the (111) crystal face; when the content of FeS in the growth system continue increased, the growth rate of crystal down to 1mg/h, and the epitaxial growth of crystal became difficultly. At the meanwhile, the ratio of diamond growth rates on the (100) face is greatly larger then the (111) face, resulting in the morphology of S-doping diamond changed from cub-octahedral to octahedral.By co-doped crystal growth experiments, it found that when B/S (B, S atomic ratios)≈0.4, high-quality golden color of crystals will be obtained; when the B/S<0.4, the color of crystals mainly by the S-related defects, with growth pits appear in (100) face easily; when the B/S>0.4, the color of crystals mainly by the B-related defects, with growth pits appear in (111) face easily.EDS shows that there was a little amounts of S element presence in the crystals. Spectroscopic characterization of sulfur-synthesized diamonds by means of Raman and infrared absorption microscopy has been made. It was found that there were appeared a strong raman peak at 1332cm-1 and a little weak raman peak at 1540cm-1. The infrared absorption microscopy spectra of diamonds were found that the crystals contain nitrogen impurity in the from of C substitutes with concentration from approximately 50 up to 600 at. ppm. An sbsroption band with a maximum at 1050cm-1, whose origin is not clear, was observed in the IR spectra.