Patent ID: 6129900
Filing Date: 2000-10-10
Classification: B01J

Abstract:
In a process for synthesis of colorless and transparent diamond single crystals containing metal in an amount of at most 0.5 weight %, N in an amount of at most 0.1 ppm and B in an amount of 0.1 to 0.6 ppm by the temperature gradient method which employs diamond as a carbon source, a solvent metal and a seed crystal, wherein the carbon source is separated from the seed crystal by a solvent metal, wherein said carbon source dissolves in said solvent metal upon heating, a temperature gradient exists between the carbon source and seed crystal and temperature and pressure are such as to permit diamond crystal growth on said seed crystal, the improvement consisting essentially of:(a) a solvent for crystal growth of an alloy containing Fe and at least one member selected from the group consisting of Co, Ni, Mn and Cr, said solvent further containing 0.1 to 6 wt. % carbon;(b) a nitrogen getter for removing nitrogen in the solvent of at least one metal selected from the group consisting of Ti, Zr, Hf, V, Nb and Ta, in a proportion of from 0.5 to 7% by weight based on the solvent;(c) a low viscosity element which is at least one member selected from the group consisting of Al, Sn, In, Ga, Ag, Cu, Cs, Pb, Sb and Zn, in an amount of from 0.5 to 3% by weight based on the solvent and(d) the crystal growth rate being higher than 2 mg/hr.