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Large diamond single crystals doped with NiS are synthesized under high pressure and high temperature. It is found that the effects on the surface and shape of the synthesized diamond crystals are gradually enhanced by increasing the NiS additive amount. It is noted that the synthesis temperature is necessarily raised to 1280°C to realize the diamond growth when the additive amount reaches 3.5% in the synthesis system. The results of Fourier transform infrared spectroscopy (FTIR) demonstrate that S is incorporated into the diamond lattice and exists in the form of C–S bond. Based on the FTIR results, it is found that N concentration in diamond is significantly increased, which are ascribed to the NiS additive. The analysis of x-ray photoelectron spectroscopy shows that S is present in states of C–S, S–O and C–S–O bonds. The relative concentration of S compared to C continuously increases in the synthesized diamonds as the amount of additive NiS increases. Additionally, the electrical properties can be used to characterize the obtained diamond crystals and the results show that diamonds doped with NiS crystals behave as n-type semiconductors. [ABSTRACT FROM AUTHOR]

In order to synthesize high-quality type-IIa large diamond, the selection of catalyst is very important, in addition to the nitrogen getter. In this paper, type-IIa large diamonds are grown under high pressure and high temperature (HPHT) by using the temperature gradient method (TGM), with adopting Ti/Cu as the nitrogen getter in Ni70Mn25Co5 (abbreviated as NiMnCo) or Fe55Ni29Co16 (abbreviated FeNiCo) catalyst. The values of nitrogen concentration (Nc) in both synthesized high-quality diamonds are less than 1 ppm, when Ti/Cu (1.6 wt%) is added in the FeNiCo or Ti/Cu (1.8 wt%) is added in the NiMnCo. The difference in solubility of nitrogen between both catalysts at HPHT is the basic reason for the different effect of Ti/Cu on eliminating nitrogen. The nitrogen-removal efficiency of Ti/Cu in the NiMnCo catalyst is less than in the FeNiCo catalyst. Additionally, a high-quality type-IIa large diamond size of 5.0 mm is obtained by reducing the growth rate and keeping the nitrogen concentration of the diamond to be less than 1 ppm, when Ti/Cu (1.6 wt%) is added in the FeNiCo catalyst. [ABSTRACT FROM AUTHOR]

This paper reports the crystal growth of diamond from the FeNi–Carbon system with additive phosphorus at high pressures and high temperatures of 5.4–5.8 GPa and 1280–1360 °C. Attributed to the presence of additive phosphorus, the pressure and temperature condition, morphology, and color of diamond crystals change obviously. The pressure and temperature condition of diamond growth increases evidently with the increase of additive phosphorus content and results in the moving up of the V-shape region. The surfaces of the diamonds also become coarse as the additive phosphorus added in the growth system. Raman spectra indicate that diamonds grown from the FeNi-phosphorus-carbon system have more crystal defects and impurities. This work provides a new way to enrich the doping of diamond and improve the experimental exploration for future material applications. [ABSTRACT FROM AUTHOR]

In spite of major progress in the science and technology of diamond growth, large-scale commercial production of gem-quality, large, single-crystal diamonds has not been feasible. Recently, we easily synthesized various types of gem-quality, large, single-crystal diamonds (Ib, IIa, and IIb) using a cubic high-pressure apparatus (performance enhanced by new design of double bevel hybrid anvil). Our solution saves the cost associated with the presses need, increases the region of synthesis of gem-quality, large, single-crystal diamonds, and decreases the effects of fluctuations of the pressure or temperature in the cubic sample cell. In addition, the quality and electrical properties of synthetic diamonds have been studied in detail. The synthetic diamonds have been successfully applied as diamond anvils or jewelry. This represents a relatively simple, inexpensive, and effective solution for commercial production and scientific research on gem-quality, large, single-crystal diamonds using a cubic high-pressure apparatus. Large-scale commercial production of gem-quality diamonds has not been feasible. Recently, we easily synthesized various types of gem-quality diamonds using CHPA, whose performance is enhanced by new design of a double bevel hybrid-anvil. The quality and electrical properties of synthetic diamonds have been studied in detail. The synthetic diamonds have been successfully applied as diamond anvils or jewelry. [ABSTRACT FROM AUTHOR]