Process for the synthesis of diamond

Details Process for the synthesis of diamond Process for the synthesis of diamond

1994-09-16

2000-10-10

Griffin, Steven P.

Chemistry of inorganic compounds

Carbon or compound thereof

Elemental carbon

B01J 306

Patent

active

061299006

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a process for the synthesis of transparent diamond single crystal suitable for use as a material for decoration and optical parts, and more particularly, it is concerned with a process for the synthesis of diamond at a static high pressure and high temperature, specifically high purity, nitrogen-free, colorless and transparent diamond of IIa type.


TECHNICAL BACKGROUND

At the present time, commercially available diamond for decoration is a colorless and tranparent diamond with little internal defects is selected from those mined in South Africa or Soviet and thus marketed. Natural decorative diamond, among jewels, is on sale in the largest amounts. As an optical part using diamond, there are IR anvil cells, laser window materials, etc. and in any case, a diamond having no absorption of light in the infrared range, called IIa type, is selected from natural gem stones and used. However, the mining amount of color-less and transparent gem stones is very small, thus resulting in problems on stable supply and price.
That is, natural diamond has the disadvantage that a transparent and colorless rough stone is mined in a small amount and is thus expensive. Above all, the output of a rough stone having no absorption of nitrogen in the infrared range is so little as represented by, for example, an output of the above described IIa type of 1-2% based on the whole rough stones, thue resulting in a problem on supply thereof. In particular, a large-sized window material of 8 mm in diameter is hardly available.
Transparent and colorless diamond has first been synthesized in artificial manner in the 1970s. This synthesis was carried out by the temperature gradient method using a Fe-3.about.5 wt % Al alloy as a solvent metal, thus obtaining several diamond crystals with 0.7.about.1.0 carat in the form of brilliant. The resulting diamond was estimated as G to H by the color scale of natural gem (GIA Standard: standard of gem provided by the American Gem Institute)(U.S. Pat. No. 4,073,380). However, such synthetic diamond has not been marketed because the synthesizing cost is higher than the price of diamond as natural gem.
Artificial diamond is ordinarily colord yellow because during synthesis at an ultra-high pressure and high temperature, nitrogen in a solvent is taken in the crystal lattice, but colorless and transparent diamond can be obtained by adding a nitrogen getter to the solvent. As this nitrogen getter, Al is well known as disclosed in, for example, "The Journal of Physical Chemistry", Vol. 75, No. 12 (1971), p 1838. Specifically, U.S. Pat. No. 4,034,066 discloses that colorless and transparent diamond single crystal of gem grade can be obtained by adding 3 to 5% by weight of Al to a Fe solvent.
As an example of other nitrogen getters than Al, it has been reported in "Muki-zaishitsu Kenkyujo Hokoku (Report of Inorganic Material Institute)", No. 39 (1984), page 16-19 that nitrogen in the crystal is removed by adding Ti or Zr to a solvent metal.
However, combinations capable of producing colorless diamond are only 1 Fe--Zr, 2 (Fe--Ni) alloy-Zr and 3 (Ni--Mn) alloy-Zr and no such colorless diamond can be formed with other combinations. In the above described combinations of 1 to 3, only the combination 1 of Fe--Zr is capable of giving one having no absdorption in a wavelength range of at most 500 nm. The presence of the absorption in the wavelength range of at most 500 nm means that nitrogen atoms are not completely removed.
Furthermore, it has already been reported by H. M. Strong and P. H. Cherenko in "J. Chem. Phys. 75 P 1938 (1971)" that in order to grow a colorless crystal without adding such a nitrogen getter, the growth rate should be reduced to at most 60% of the case of growing a yellow crystal of Ib type.
In particular, synthetic colorless and transparent diamond has not been produced on a commercial scale, because of higher synthesis cost thereof than that of natural decorative diamond. The reason therefor is that not only an expensive and special apparatus i

REFERENCES:
patent: 4287168 (1981-09-01), Wentorf, Jr. et al.
patent: 4425315 (1984-01-01), Tsuji et al.
patent: 4518659 (1985-05-01), Gigl et al.
Patent Abstracts of Japan; vol. 13, No. 105 (C-575) Mar. 13, 1989 & JP-A-63278545 (Sumitomo Electric Ind. Ltd.) Nov. 16, 1988.

Affiliated with

Also associated with

Rating

Process for the synthesis of diamond does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for the synthesis of diamond, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the synthesis of diamond will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2254202