Abstract
This paper reprots that with Ni-based catalyst/solvent and with a dopant of NaN3, large green single crystal diamonds with perfect shape are successfully synthesized by temperature gradient method under high pressure and high temperature in a China-type cubic anvil high-pressure apparatus (SPD-6 × 1200), and the highest nitrogen concentration reaches approximately 1214–1257 ppm calculated by infrared absorption spectra. The synthesis conditions are about 5.5 GPa and 1240–1300 °C. The growth behaviour of diamond with high-nitrogen concentration is investigated in detail. The results show that, with increasing the content of NaN3 added in synthesis system, the width of synthesis temperature region for growth high-quality diamonds becomes narrower, and the morphology of diamond crystal is changed from cube-octahedral to octahedral at same temperature and pressure, the crystal growth rate is slowed down, nevertheless, the nitrogen concentration doped in synthetic diamond increases.