Effect of metal solvents on nitrogen content in synthetic diamonds

Abstract

When growing diamond crystals with metal solvents under HPHT, if no special means to remove nitrogen impurity in crystals, the crystal color show pale yellow to green yellow according to different metal solvents. In this paper, Micro-IR absorption spectrum measurements are used to determine the nitrogen content in large synthetic diamonds grown with different metal solvents by temperature gradient method. It is found that, when a trace of additives related to dispersed nitrogen is added into the metal solvents, the nitrogen content changes obviously. For example, with Ni-based NiMnCo alloy as metal solvent, the nitrogen content in diamond crystals is about 400 × 10-6; but with Fe - based FeNiCo alloy, the content is about 150 × 10-6. However, when NaN3(lwt‰) is added into the metal solvents, whether Fe - based or Ni - based catalyst was used, the nitrogen content in diamonds increase to about 700 × 10-6, this means that a trace of additives in the catalyst can influence the growth characters of crystals remarkably. Show more