Growth of Large High-Quality Type-II a Diamond Crystals

Large high-quality type-II a diamond crystals in size of about 4.0mm have been grown under the condition of 5.5GPa and 1200--1300°C by using the temperature gradient method in a domestic cubic anvil high-pressure apparatus. The Fe₅₅Co₁₆Ni₂₅ alloy (KOV) is used as the solvent metal, and Ti with the content 1.5wt.% of the solvent metal is selected as the nitrogen getter to reduce the impurity of nitrogen in the diamond crystal. To avoid the impurities and cave in the crystal, the growth rate of the initial stage of the growing process is controlled within 0.45mg/h and the ring carbon source of the size Ф8mm-Ф6mm×3mm is used to grow large diamond crystals.