Method for Synthesizing Gem Grade Colorless Diamonds by Seed Crystal Method

The invention discloses a method for synthesizing gem grade colorless diamonds by seed crystal method, which comprises the following steps: (1) FeMnCo is used as a catalyst sheet, graphite is used asa carbon source, and Cu foil is used as a nitrogen removal agent, seed crystal is embedded on a crystal bed, the upper end surface of the seed crystal and the upper end surface of the crystal bed areflush, and the raw materials are assembled to synthesize a block; (2) then the high temperature and high pressure synthesis is started, and the pressure is increased to be 60-70MPa in 0-200s at a uniform speed, then the pressure is kept for 2000-3000s, and then the pressure rises to 90-100MPa in 80-120s at a uniform speed; the heating power is increased to be 2.5-3.5 KW in 0-400s at a uniform speed, then kept for 2000-3000s, and then increased to 5-6KW at a uniform speed in 500-800 seconds. The power and pressure are kept until the time is 10000 seconds, and then the power and pressure are gradually reduced and then gr