Observation of Surface Microstructure of HPHT Synthetic Diamond Crystals and Genesis Discussion

Abstract

BACKGROUND As the world's largest producer of synthetic diamonds, China accounts for more than 90% of the world's total production, of which high pressure-high temperature (HPHT) synthetic diamonds are dominant. Previous scholars have conducted many studies on analytical methods and property analysis of HPHT synthetic diamonds. However, the research on the pickling process after the growth of HPHT synthetic diamonds and the internal and external micro-structures after pickling is still insufficient. OBJECTIVES To characterize 118 synthetic diamonds produced in China by high temperature and high pressure method. METHODS The HPHT synthetic diamonds were observed by laser scanning confocal microscopy (LSCM) and ultra-depth-of-field 3D microscopy, and the dark inclusions in these micro-structures were qualitatively analyzed by laser Raman spectroscopy. RESULTS Three structure types were found. Step-like growth structures with certain angles revealed the crystallographic characteristics of HPHT synthetic diamond poly-crystals. Near-parallel linear scratches reflected the contact relationship between diamond grains in the growth chamber. The 'rope-tied' structures reflected the growth rate of HPHT synthetic diamonds. CONCLUSIONS The micromorphology of these diamond surfaces reflects the growth conditions and environment of HPHT synthetic diamond gradient high temperature and continuous high pressure, which is of significance for the identification of HPHT synthetic diamonds.

Keywords

• synthetic diamond
• high pressure-high temperature
• micro-structure
• laser scanning confocal microscopy
• crystal growth rate