Effect of CH₆N₄O Additive on Ib-Type Diamond from Ni-Based Alloy under HPHT Conditions

Area of Science:

• Materials Science
• Geochemistry
• Crystallography

Background:

• Natural diamonds contain elements like carbon, hydrogen, oxygen, and nitrogen, present in their growth environment.
• Replicating the C-H-O-N system is crucial for understanding natural diamond formation.
• Previous studies focused on the elemental composition of natural diamond inclusions.

Purpose of the Study:

• To synthesize diamond crystals within a controlled C-H-O-N system.
• To investigate the influence of an organic additive on diamond growth and defect formation.
• To analyze the incorporation of nitrogen, oxygen, and hydrogen into synthesized diamonds.

Main Methods:

• High-pressure and high-temperature synthesis in a NiMnCo-C system with carbohydrazide additive.
• Characterization using optical microscopy (OM), Raman spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS).

Main Results:

• Successfully synthesized diamond crystals at 1280–1320 °C and 5.4–6.0 GPa.
• Observed new extended defects resembling dislocations, perpendicular to the {111} face, induced by the additive.
• Confirmed high-quality sp³ structures in synthesized diamonds via Raman and XRD.
• FTIR analysis revealed nitrogen content variations with synthesis temperature and pressure.
• XPS confirmed the successful incorporation of N, O, and H into the diamond lattice.

Conclusions:

• The C-H-O-N system, using carbohydrazide, enables diamond synthesis mimicking natural conditions.
• The organic additive influences defect formation and nitrogen incorporation.
• Synthesized diamonds exhibit high structural quality, with incorporated N, O, and H, providing insights into natural diamond genesis.